6576750

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C. 20460

OFFICE OF THE ADMINISTRATOR
SCIENCE ADVISORY BOARD March 6, 2009

EPA-CASAC-09-005

The Honorable Lisa P. Jackson

Administrator U.S. Environmental Protection Agency 1200 Pennsylvania Avenue, N.W. Washington, D.C. 20460

Subject: Consultation on Ambient Air Mon itoring Issues Related to the Ozone NAAQS

Dear Administrator Jackson:

The Clean Air Scientific Advisory Co mmittee (CASAC) Ambient Air Monitoring & Methods Subcommittee held a public teleconference on February 10, 2009, to consult with staff from EPA’s Office of Air Quality Planning and Standards (OAQPS) on monitoring network design issues related to the National Ambient Air Quality Standards (NAAQS) for ozone (O 3 ) as promulgated in March 2008. The final rule re vised both the primary and secondary standards and set identical, 8-hour standard s of 0.075 ppm for both public health and welfare. The Agency is developing separate rules to support change s in the monitoring network requirements based on the revisions of the primary and secondary NAA QS and considering changes to the required ozone monitoring seasons.

The CASAC uses a consultation as mechanism for technical experts to provide comments to the Agency on the issues under consideration. In general, the Subcom mittee is supportive of the Agency’s efforts to increase the number O 3 monitors; however, as noted in the individual comments enclosed with this letter, outlying issu es with deployment, siting, and state-specific coverage remain. As this is a consultation, we do not expect a formal response from the Agency. We thank the Agency for the opportunity to pr ovide advice in the NAAQS review process.

Sincerely,

/Signed/

Dr. Armistead (Ted) Russell, Chair

CASAC AAMMS

EnclosuresEnclosure A

U.S. Environmental Protection Agency Clean Air Scientific Advisory Committee Ambient Air Monitoring and Methods Subcommittee

CASAC MEMBERS Dr. Armistead (Ted) Russell (Chair) , Professor, Department of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA

Dr. Donna Kenski , Data Analysis Director, Lake Mi chigan Air Directors Consortium,
Rosemont, IL

SUBCOMMITTEE MEMBERS Mr. George A. Allen , Senior Scientist, Northeast States for Coordinated Air Use Management (NESCAUM), Boston, MA

Dr. Judith Chow , Research Professor, Desert Research Institute, Air Resources Laboratory, University of Nevada, Reno, NV

Mr. Bart Croes , Chief, Research Division, California Air Resources Board, Sacramento, CA

Dr. Kenneth Demerjian , Professor and Director, Atmospheri c Sciences Research Center, State University of New York, Albany, NY

Dr. Delbert Eatough , Professor of Chemistry, Department of Chemistry and Biochemistry , Brigham Young University, Provo, UT

Dr. Eric Edgerton , President, Atmospheric Research & Analysis, Inc., Cary, NC

Mr. Henry (Dirk) Felton , Research Scientist, Division of Ai r Resources, Bureau of Air Quality Surveillance, New York State Department of Environmental Conservation, Albany, NY

Dr. Philip Hopke , Bayard D. Clarkson Distinguished Pr ofessor, Department of Chemical Engineering, Clarkson University, Potsdam, NY

Dr. Rudolf Husar , Professor, Mechanical Engineeri ng, Engineering and Applied Science, Washington University, St. Louis, MO

Dr. Kazuhiko Ito , Assistant Professor, Department of Environmental Medicine, School of Medicine, New York University, Tuxedo, NY

Dr. Thomas Lumley , Associate Professor, Biostatistics, School of Public Health and Community Medicine, University of Washington, Seattle, WA

2Dr. Peter H. McMurry , Professor and Head, Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN

Mr. Richard L. Poirot , Environmental Analyst, Air Pollutio n Control Division, Department of Environmental Conservation, Vermont Agency of Natural Resources, Waterbury, VT

Dr. Kimberly A. Prather ,* Professor, Department of Chemis try and Biochemistry, University of California, San Diego, La Jolla, CA

Dr. Jay Turner , Visiting Professor, Crocker Nuclear Laboratory, University of California, Davis, CA

Dr. Warren H. White , Research Professor, Crocker Nu clear Laboratory, University of California - Davis, Davis, CA

Dr. Yousheng Zeng , Air Quality Services Director, Pr ovidence Engineering & Environmental Group LLC, Baton Rouge, LA

Dr. Barbara Zielinska , Research Professor, Division of At mospheric Sciences, Desert Research Institute, Reno, NV

SCIENCE ADVISORY BOARD STAFF Ms. Kyndall Barry , Designated Federal Officer, 1200 Penns ylvania Avenue, N.W. (Mailcode 1400F), Washington, DC, Phone: 202-343-9868, Fax: 202-233-0643, ( barry.kyndall@epa.gov )

*Dr. Prather did not participate in this CASAC AAMM Subcommittee activity.

3Enclosure B

Comments received:

Mr. George Allen .......................................................................................................................... 5

Dr. Judith C. Chow ....................................................................................................................... 8

Mr. Bart Croes ............................................................................................................................ 15 Dr. Delbert J. Eatough ................................................................................................................ 18

Mr. Dirk Felton ........................................................................................................................... 21 Dr. Phil K. Hopke ........................................................................................................................ 24

Dr. Rudolf Husar ........................................................................................................................ 27

Dr. Kazuhiko Ito ......................................................................................................................... 28

Dr. Donna Kenski ........................................................................................................................ 31 Dr. Thomas Lumley .................................................................................................................... 34 Dr. Peter H. McMurry ................................................................................................................ 37

Mr. Richard L. Poirot ................................................................................................................. 40

Dr. Armistead Russell ................................................................................................................. 44 Dr. Jay R. Turner ........................................................................................................................ 46

Dr. Warren H. White .................................................................................................................. 49 Dr. Yousheng Zeng ..................................................................................................................... 50

Dr. Barbara Zielinska ................................................................................................................. 52

4

### Mr. George Allen

Urban Network Design Requirements

1. Considering the ozone minimum monitoring requirements that are already promulgated through 40 CFR Part 58, is the considered change to these requirements sufficient to ensure a minimally adequate network in urban areas?

Yes, these changes should result in an urban netw ork that is “minimally adequate”. Most urban areas are “ozone holes” due to NO scavenging; excep tions to this are very large urban areas such as NYC and LA. Still, urban ozone is an important monitoring need.

2. We are considering a timeline that would require newly required ozone monitors to be operational no later than January 1, 2011, based on the expectation that final rulemaking will be completed in 2009. Is this schedule appropriate or should EPA consider providing an additional year for new monitors to be deployed (or re located)? What would be the advantages or disadvantages of a stagger ed deployment schedule?

While it is desirable to deploy ne twork changes sooner than later, State, Local and Tribal Air Agencies (“SLT”) are presently under substant ial pressure to meet other required new monitoring such as NCore. At the same ti me, these agencies are under severe budgetary constraints that effect staffing leve ls, and this is expected to conti nue for the near future. To the

extent that it does not adve rsely impact compliance design ation, a staggered deployment schedule that extends the period for another year would probably be helpful to air agencies.

Non-Urban Network Design Requirements

1. We are considering a new requirement that each State operate a minimum of three non-urban ozone monitors to meet certain objectives (descr ibed above). Considering the stated objectives of the non-urban ozone monitoring requirements, is three required monitors per state sufficient?

Specifying this on a per state basis may not be the best way. Three may be excessive for RI and

insufficient for TX. There are additional variable s that could drive this need on a regional basis such as regional transport, transport over large bodies of water (allowing formation without sinks), etc. In general, for a pollutant like oz one that is often regiona lly transported, requiring any component of network siting design on a state by state basis may not be the best approach. A design that is relatively ignorant of state boundaries may be better.

2. What factors should be considered in the si ting of ozone monitors to assess impacts on ozone sensitive vegetation in na tional parks, wilderness areas, and other ecosystems?

Site elevation and over-water transport are two fact ors that may need to be considered. Distance downwind from major precursor sources could be another.

53. In addition to the objectives that have b een described for non-urban ozone monitors, what other objectives should be consid ered in the final network desi gn? How would the consideration of additional objectives, if any, effect the minimum number of non-urban required monitors?

In these resource constrained times, a careful balance between meeting network objectives and the resources required to implement additional monitoring must be met.

4. Current ozone monitoring regulations (descr ibed in Appendix E of 40 CFR part 58) include requirements for station and probe siting (e.g., ver tical distance of inle ts, set-back distances from roadways). Are these requirements (t hat have been developed for urban monitors) appropriate for non-urban ozone monitors? Wh at changes, if any, should be considered?

Setbacks from roadways or other local sources th at may impact measured ozone may need to be increased, since non-urban ozone site are presumably regional in spatial scale.

5. We believe that States should have the opt ion of designating that existing non-urban ozone monitors that are potentially operated by anot her agency (e.g., CASTNET monitors operated by the National Park Service) be utilized for meeting certain non-urban minimum monitoring requirements. What factors should States use to determine if such m onitors are appropriate to

include in their networks?

Any existing or future “third party” ozone sites should meet all siting and operational QC requirements required of SLT sites if data from those sites is going into AQS and would be used for meeting required network design goals and NAAQS compliance purposes.

Ozone Monitoring Season

1. We are considering changes to the required ozone monitoring seasons based on analyses of the patterns of ozone exceedances and occurrences of the Modera te level of the Air Quality Index, during periods outside of the currently re quired seasons. What other factors should be considered, if any, in the determination of the le ngth of the required monitoring season for each

State?

First, for something like the 50 largest cities, or perhaps locations of the 54 core STN sites, ozone should be measured year round for use in health effect studies. NCore will presumably provide this. For other sites, it may be difficult to determine an appropriate season from existing data if there are no year-round or extended season s ite data presently available that represent a given area. In these cases, an analysis of se veral year’s worth of st art and end ozone season months’ data is the best that can be done; if there is a reasonable chance of an exceedance occurring outside of the current season, then the required monitoring season should be extended by at least one month. In the northeast US for example, it is clear that March needs to be

included in the revised season. March has subs tantial solar radiation, and “leaf-out” does not occur until early May. These and perhaps other f actors contribute to high observed ozone levels during that month from the limite d year-round network currently in pl ace. It is less likely that

October needs to be included for this northeast ex ample, since solar radiation is less than in

6March. Still, for some northeast states, Octobe r may be appropriate to include in the ozone monitoring season.

2. We believe that ozone monito rs that are located at NCore stations should be operated on a year-round monitoring schedule. Under what circ umstances might it be a ppropriate to require year-round monitoring at other stations beside NCore?

It might be informative for certain sites such as high-elevation transport locations to run yearround. Stratospheric intrusion can oc cur, and there is a level of ozone present that is of interest (from a non-compliance perspective) even in th e winter. Another possible need for year-round monitoring might be the situati on observed in Wyoming’s Upper Green River Basin, where there are intensive natural gas wells in valley locations . It appears that the reported winter ozone is

real and not an interference w ith the UV monitoring method; situ ations like these have the potential for increasing our understanding of oz one formation in non-traditional scenarios like this with cold temperatures and decreased incomi ng solar radiation. A rela ted issue here is the

lack of a viable commercial instrument for the EPA ozone reference method (chemiluminescent ethylene). Perhaps it is time for EPA to consider a new reference method that is reasonably free from interferences (Hg, VOCs, water vapor, etc) a nd is commercially available. Finally, if an

ozone monitor is at a site where other monito rs are run year-round, the incremental cost to continue ozone for the full year is relatively small, and the potentia l value for non-compliance use may turn out to be substantial. The significa nt cost-savings of turning off an ozone monitor

for a few months is limited to sites wher e ozone is the only pollutant measured.

3. We are considering that changes to the re quired ozone monitoring season be applicable to existing monitors beginning in 2010, one year ahe ad of the deployment schedule for newly required ozone monitors. Is this sc hedule reasonable for existing monitors?

Yes it is reasonable. For existing monitors, extending the season by a month or two does not have a large impact on SLT agency resources.

7

### Dr. Judith C. Chow

Urban Network Design Requirements

1. Considering the ozone minimum monitoring re quirements that are already promulgated through 40 CFR Part 58, is the considered change to these requirements sufficient to ensure a minimally adequate network in urban areas?

Figure 1 of the Ozone monitoring document shows that there are many populated but unmonitored areas. Many of these areas have experienced substantial population and traffic growth, especially in the west ern and southeastern U.S. There is ample evidence that O 3 is transported over long-distances, as well as be ing locally generated, and that elevated concentrations can be found nearly everywhere (Bertschi and Jaffe, 2005; Choi et al., 2008; Dabdub et al., 1999; Goldstein et al ., 2004; Guttorp et al., 1994; Hu dman et al., 2004; Rao et al., 2003; Rosenthal et al., 2003; Spicer et al., 1979; Wolff et al., 1977). Elevated O 3 can also be generated by non-urban sources such as plantlife (Marr et al., 2002; Pun et al., 2002; Tao et al., 2003), fires (Bertschi and Jaffe, 200 5; Preisler et al., 2005), and liv estock (Howard et al., 2008). It is entirely appropriate to lower the population threshold for m onitoring to protect urban public

health.

2. We are considering a timeline that would re quire newly required ozone monitors to be operational no later than January 1, 2011, based on the expectation that final rulemaking will be completed in 2009. Is this schedule appropriate or should EPA consider providing an additional year for new monitors to be deployed (or re located)? What would be the advantages or disadvantages of a stagger ed deployment schedule?

Maximum flexibility should be allowed for the ad dition of monitoring locations. It is better to: 1) thoroughly evaluate the potential measuremen t locations, 2) procure and install the best equipment, 3) train operators in its use, and 4) have an adequate shakedown period than to rush the process. It often takes a y ear or more to obtain the funding, permits, and infrastructure when a new air quality site is installed.

Non-Urban Network Design Requirements

1. We are considering a new require ment that each State operate a minimum of three non-urban ozone monitors to meet certain objectives (descr ibed above). Considering the stated objectives of the non-urban ozone monitoring requirements, is three required monitors per state sufficient?

It is not clear whether or not th is would require three monitors in addition to those identified in Figure 2 of the Ozone monitoring document or w ould include those monitors. Perhaps columns

could be added to Table 2 of the Ozone monito ring document that would include the number of current monitors in each state that are: 1) fede ral lands with sensitive ecosystems; 2) small towns (micropolises?); and 3) non-urban locations with e xpected high concentrations. Would this also

8include existing monitors from non-compliance ne tworks (e.g., the National Park Service’s 2B

O 3 monitors http://www.nature.nps.gov/ air/Studies/portO3.cfm )? Looking at the large differences in areas of different states, the comp lex terrain in some stat es as opposed to others, and the existing densities of m onitors in Figures 1 and 2 of the Ozone monitoring document, it

would seem that a more refined allocation of mo nitoring locations based on a conceptual model

of O 3 precursor locations, formation potential, and tr ansport corridors might be more useful than an allocation of three monitors per state.

2. What factors should be considered in the siti ng of ozone monitors to assess impacts on ozone sensitive vegetation in na tional parks, wilderness areas, and other ecosystems?

Factors for measurement location should include: 1) presence of species susceptible to damage (Legge et al., 1995; Miller and McBride, 1999; Musselman et al., 2006; Pa oletti, 2006; Prinz, 1985); 2) potential for high O 3 levels (transport, upslope/downsl ope flows, local generation) (Lee et al., 2007; Wager and Baker, 2006); and 3) logistics and cost-effec tiveness. It might be more logical and cost-effective to extend the NPS network to additional IMPROVE (http://vista.cira.colostate.edu/views) sites where some infrastructure already exists. It would also be useful to think “beyond compliance” (Chow and Watson, 2008) and not require a fullscale compliance monitoring site at some of the remote locations.

3. In addition to the objectives that have been described for non-urban ozone monitors, what other objectives should be considered in the fi nal network design? How wo uld the consideration of additional objectives, if any, effect the minimum number of non-urban required monitors?

Additional objectives should incl ude: 1) tracking trends in O 3 and precursors to evaluate accountability and relationships to other pollutants for O 3 SIPs (Cohan et al., 2007; Foley et al., 2003); 2) increasing understanding of O 3 chemistry and transport (Blanchard et al., 1999; Blanchard and Fairley, 2001; Blanchard and Stoeck enius, 2001; Milford et al., 1989; Milford et al., 1994; Sillman et al., 1997; Sillman, 1999; Si llman, 2001); 3) defining non-attainment areas according to established criteria (Clark County Department of Air Quality and Environmental Management, 2004; Seitz, 2000); and 4) for ecasting effects of climate change on O 3 concentrations (Grewe, 2007; Jacob and Winner, 2009; Zeng et al., 2008).

Additional monitors might be needed at some locations for NO 2 and certain VOCs to better attain these objectives. For some remote forest exposure locations it might be more effective to use passive O 3 monitors (Bernard et al., 1999; Grosj ean and Williams, II, 1992; Manning et al., 1996; Paoletti, 2006; Skelly et al., 2001).

4. Current ozone monitoring regulations (described in Appendix E of 40 CFR part 58) include requirements for station and probe si ting (e.g., vertical distance of inlets, set-back distances from roadways). Are these requirements (that have been developed for urban monitors) appropriate for non-urban ozone monitors? What c hanges, if any, should be considered?

9No. O 3 monitors within the forest measure lower va lues than those outside or above the forest canopy because of the plant uptake (which also ca uses the damage). Both measurement types are important, as the difference indicates the expo sure, so two nearby sites with different middlescale to neighborhood-scale characte ristics might be considered. Monitors within the shallow nighttime surface inversion often experience NO titr ation, even when they are somewhat distant from a roadway, due to the overnight trapping of po llutants. Monitors on a hilltop, tall building, or towers may better indicate O 3 exposure and carryover than surface-based monitors. It is difficult to locate sites very distant from some t ype of roadway as the sites need to be accessed regularly.

5. We believe that States shoul d have the option of designati ng that existing non-urban ozone monitors that are potentially operated by anot her agency (e.g., CASTNET monitors operated by the National Park Service) be utilized for meeting certain non-urban minimum monitoring requirements. What factors should States use to determine if such mon itors are appropriate to

include in their networks?

All available data should be compiled and used for the defined objectives. As noted above, the information needed and acquired should dictate th e number of monitors rather than an arbitrary assignment of a certain number of monitors to each state. Wher e a number of different networks or monitor types are used, there should be a comparison and eval uation of the operating conditions, including evidence of regular calibration, auditing, maintenance, precision, accuracy, and comparability.

Ozone Monitoring Season

1. We are considering changes to the required ozone monitoring seasons based on analyses of the patterns of ozone exceedances and occurrences of the Modera te level of the Air Quality Index, during periods outside of the currently re quired seasons. What other factors should be considered, if any, in the determination of the le ngth of the required monitoring season for each

State?

Some of the remote sites may not be easily acce ssible during winter owing to snow, and this should be considered. High O 3 concentrations can occur in wi nter, however, owing to reflection of sunlight from snowcover and concentration of precursors during the day within a shallow layer over the snow. O 3 is also correlated with HNO 3 (Aneja et al., 1994; Bottenheim and Sirois, 1996) that is a precursor to wintertime PM 2.5 nitrate levels and can be useful as part of a multipollutant control strategy development where PM 2.5 concentrations are also excessive.

2. We believe that ozone monitors that are located at NCore sta tions should be operated on a year-round monitoring schedule. Under what circ umstances might it be appropriate to require year-round monitoring at other stations beside NCore?

O 3 monitors should be operated year round wher ever practical to evaluate multi-pollutant approaches and to determine the extent of elevated levels during winter. This is the case already

10at most multi-pollutant monitoring sites. Ther e may be instances at remote locations where access is denied due to weather, and it is probabl y not cost-effective to take extreme measures for such locations. At a minimum they should be operated year-round in areas that experience

excessive PM 2.5 and O 3 concentrations.

3. We are considering that changes to the requ ired ozone monitoring season be applicable to existing monitors beginning in 2010, one year ahe ad of the deployment schedule for newly required ozone monitors. Is this sc hedule reasonable for existing monitors?

The same argument applies as above. It is better to phase in the changes in a logical manner than to set a mandate that will compromise quality and the utility of the data. It is probably less of a burden to extend the monitoring period than it is to locate new sites, but a dditional staff, training, and possibly instrumentation may be need ed that will require some lead time.

References

Aneja, V.P.; Claiborn, C.S.; Li, Z.; Murthy, A. ( 1994). Trends, seasonal vari ations, and analysis of high elevation surf ace nitric acid, ozone , and hydrogen peroxide. Atmos. Environ.

, 28 (10):

1781-1790.

Bernard, N.L.; Gerber, M.J.; Astre, C.M.; Saintot, M.J. (1999). Ozone measurement with passive samplers: Validation and use for ozone po llution assessment in Montpellier, France.

Environ. Sci. Technol.

, 33 (2): 217-222.
Bertschi, I.T.; Jaffe, D.A. (2005). Long-range transport of ozone, carbon monoxide, and aerosols to the NE Pacific troposphere during the summ er of 2003: Observations of smoke plumes

from Asian boreal fires. J. Geophys. Res. -Atmospheres

, 110 (D5):

Blanchard, C.L.; Lurmann, F.W.; Roth, P.M.; Je ffries, H.E.; Korc, M. (1999). The use of ambient data to corroborate analys es of ozone control strategies. Atmos. Environ.

, 33 (3):

369-381.
Blanchard, C.L.; Fairley, D. (2001). Spatial mapping of VOC and NOx-limitation of ozone

formation in central California. Atmos. Environ.

, 35 (22): 3861-3873.
Blanchard, C.L.; Stoeckenius, T. (2001). Ozone response to precursor controls: Comparison of data analysis methods with the predictions of photochemical air quality simulation models.

Atmos. Environ.

, 35 (7): 1203-1215.
Bottenheim, J.W.; Sirois, A. (1996). Long-term daily mean mixing ratios of O-3, PAN, HNO3, and particle nitrate at a rural location in eas tern Canada: Relationships and implied ozone production efficiency. J. Geophys. Res. -Atmospheres

, 101 (D2): 4189-4204.
Choi, Y.; Wang, Y.; Zeng, T.; Cunnold, D.; Yang, E.S.; Martin, R.; Chance, K.; Thouret, V.; Edgerton, E. (2008). Springtime transitions of NO2, CO, and O-3 over North America: Model evaluation and analysis. J. Geophys. Res. -Atmospheres

, 113 (D20):
Chow, J.C.; Watson, J.G. (2008). New directions : Beyond compliance air quality measurements.

Atmos. Environ.

, 42 (21): 5166-5168. doi:10.1016/j.atmosenv.2008.05.004.
Clark County Department of Air Quality and Environmental Management (2004). Nevada air quality designations boundary recommendations for the 8-hour ozone NAAQS for Clark County, Nevada. prepared by Cl ark County Department of Ai r Quality and Environmental

11Management, Las Vegas, NV, http://www.epa.gov/ozonedesignations/documents/clark/NV/boundary.pdf
Cohan, D.S.; Boylan, J.W.; Marmur, A.; Khan, M.N. (2007). An integrated framework for multipollutant air quality management and its application in Georgia. Environmental Management

, 40 (4): 545-554.
Dabdub, D.; DeHaan, L.L.; Seinfeld, J.H. (1999). Analysis of ozone in the San Joaquin Valley of

California. Atmos. Environ.

, 33 (16): 2501-2514.
Foley, G.J.; Georgopoulos, P.G.; Lioy, P.J. (2003). Accountability within new ozone standards.

Environ. Sci. Technol.

, 37 (21): 392A-+.
Goldstein, A.H.; Millet, D.B.; Mckay, M.; Jaegle , L.; Horowitz, L.; Cooper, O.; Hudman, R.; Jacob, D.J.; Oltmans, S.; Clarke, A. (2004). Im pact of Asian emissions on observations at Trinidad Head, California, during ITCT 2K2. J. Geophys. Res. -Atmospheres

, 109 (D23):
Grewe, V. (2007). Impact of climate variability on tropospheric ozone. Sci. Total Environ.

, 374 (1): 167-181.
Grosjean, D.; Williams, E.L., II (1992). Field tests of a passive sampler for atmospheric ozone at

California mountain forest locations. Atmos. Environ.

, 26A (8): 1407-1411.
Guttorp, P.; Meiring, W.; Sampson, P.D. (1994). A space-time analysis of ground-level ozone

data. Environmetrics

, 5 (3): 241-254.
Howard, C.J.; Yang, W.; Green, P.G.; Mitloehner, F.; Malkina, I.L.; Floc chini, R.G.; Kleeman, M.J. (2008). Direct measurements of the oz one formation potential from dairy cattle emissions using a transportable smog chamber. Atmos. Environ.

, 42 (21): 5267-5277.
Hudman, R.C.; Jacob, D.J.; Cooper, O.R.; Evans, M.J.; Heald, C.L.; Park, R.J.; Fehsenfeld, F.; Flocke, F.; Holloway, J.; Hubler, G.; Kita, K.; Koike, M.; Kondo, Y.; Neuman, A.; Nowak, J.; Oltmans, S.; Parrish, D.; Roberts, J. M.; Ryerson, T. (2004). Ozone production in transpacific Asian pollution plumes and impli cations for ozone air quality in California. J. Geophys. Res. -Atmospheres

, 109 (D23): D23S10. doi:10.1029/2004JD004974.
Jacob, D.J.; Winner, D.A. (2009). Effect of climate change on air quality. Atmos. Environ.

, 43 (1): 51-63.
Lee, S.M.; Fernando, H.J.S.; Grossman-Clarke, S. (2007). MM5-SMOKE-CMAQ as a modeling tool for 8-h ozone regulatory enforcement: application to the state of Arizona. Environmental Modeling & Assessment

, 12 (1): 63-74.
Legge, A.H.; Grunhage, L.; Nosal, M.; Jager, H.J.; Krupa, S.V. (1995). Ambient ozone and adverse crop response: An evaluation of North Am erican and European data as they relate to exposure indices and critical levels. Journal of Applied Botany-Angewandte Botanik

, 69 (5- 6): 192-205.
Manning, W.J.; Krupa, S.V.; Bergweiler, C.J.; Nels on, K.I. (1996). Ambient ozone (O3) in three

Class I wilderness areas in the northeastern USA: Measurements with Ogawa passive samplers. Environ. Poll.

, 91 (3): 399-403.
Marr, L.C.; Noblet, G.S.; Harley, R.A. (2002) . Formation of photochemical air pollution in central California 2. Impact of revise d emissions on Eulerian model predictions. J. Geophys.

Res.

, 107 (D6): 6-1-6-11.
Milford, J.B.; Russell, A.G.; McRae, G.J. (1989). A new approach to photochemical pollution control: Implications of spatial patterns in pollutant responses to reductions in nitrogen oxides and reactive organic gas emissions. Enivron. Sci. Technol.

, 23 1290-1299.

12Milford, J.B.; Gao, D.; Sillman, S.; Blossey, P.; Russell, A.G. (1994). NO y as an indicator of the sensitivity of ozone to ROG and NO

x emissions. J. Geophys. Res.

, 99 (D2): 3533-3542.
Miller, P.R.; McBride, J.R. (1999). Oxidant Air Pollution Impacts in the Montane Forests of Southern California. A Case Study of the San Bernardino Mountains . Ecological Studies 134; Springer-Verlag: New York.

Musselman, R.C.; Lefohn, A.S.; Massman, W.J. ; Heath, R.L. (2006). A critical review and analysis of the use of exposure- and flux- based ozone indices fo r predicting vegetation

effects. Atmos. Environ.

, 40 (10): 1869-1888.
Paoletti, E. (2006). Impact of ozone on Mediterranean forests: A review. Environ. Poll.

, 144 (2):

463-474.
Preisler, H.K.; Grulke, N.E.; Bytnerowicz, A.; Es peranza, A. (2005). Analyzing effects of forest fires on diurnal patterns of ozone concentrations. Phyton-Annales Rei Botanicae

, 45 (4): 33-

39.
Prinz, B. (1985). Effects of air pollution on forests - Critical review. J. Air Poll. Control Assoc.

, 35 (9): 913-915.
Pun, B.K.; Wu, S.Y.; Seigneur, C. (2002). Contribu tion of biogenic emissions to the formation of ozone and particulate matter in the eastern United States. Environ. Sci. Technol.

, 36 (16):

3586-3596. DOI: 10.1021/es015872v.
Rao, S.T.; Ku, J.Y.; Berman, S.; Zhang, K.S.; Ma o, H.T. (2003). Summertime characteristics of the atmospheric boundary layer and relationships to ozone levels over the eastern United

States. Pure and Applied Geophysics

, 160 (1-2): 21-55.
Rosenthal, J.S.; Helvey, R.A.; Battalino, T.E.; Fisk, C.; Greiman, P.W. (2003). Ozone transport by mesoscale and diurnal wind circula tions across southern California. Atmos. Environ.

, 37 S51-S71.
Seitz, J.S. (2000). Boundary guidance on air qual ity designations for the 8-hour ozone national ambient air quality standards. prepared by U.S. Environmental Protection Agency, Research Triangle Park, NC,

Sillman, S.; He, D.; Cardelino, C.A.; Imhoff, R. E. (1997). The use of photochemical indicators

to evaluate ozone-NO

x - hydrocarbon sensitivity: Case st udies from Atlanta, New York, and Los Angeles. J. Air Waste Manage. Assoc.

, 47 (10): 1030-1040.
Sillman, S. (1999). The erroneous use of receptor modeling to diagnose O 3 -NO X -hydrocarbon sensitivity. Atmos. Environ.

, 33 (14): 2289-2291.
Sillman, S. (2001). Comment on 'The impact of an 8h ozone air quality standard on ROG and NOX controls in southern California' by Chock et al. Atmos. Environ.

, 35 (19): 3367-3369.
Skelly, J.M.; Ferdinand, J.A.; Savage, J.E.; Ja godzinski, J.M.; Mulik, J.D. (2001). A 13-week comparison of passive and continuous ozone mo nitors at forested sites in north-central Pennsylvania. J. Air Waste Manage. Assoc.

, 51 (9): 1280-1287.
Spicer, C.W.; Joseph, D.W.; Sticksel, P.R.; War d, G.F. (1979). Ozone sources and transport in

the northeastern United States. Enivron. Sci. Technol.

, 13 (8): 975-985.

Tao, Z.N.; Larson, S.M.; Wuebbles, D.J.; W illiams, A.; Caughey, M. (2003). A summer simulation of biogenic contribu tions to ground-level ozone ov er the continental United

States. J. Geophys. Res. -Atmospheres

, 108 (D14):
Wager, D.J.; Baker, F.A. (2006). Ozone concentr ations in the Central Wasatch Mountains of

Utah. J. Air Waste Manage. Assoc.

, 56 (10): 1381-1390.

13Wolff, G.T.; Lioy, P.J.; Wight, G.D. ; Meyers, R.E.; Cederwall, R.T. (1977). An investigation of long-range transport of oz one across the midwestern and eastern United States. Atmos.

Environ.

, 11 797-802.
Zeng, G.; Pyle, J.A.; Young, P.J. (2008). Impact of climate change on tropospheric ozone and its global budgets. Atmos. Chem. Phys.

, 8 (2): 369-387.

14

### Mr. Bart Croes

These comments also reflect input from Califor nia Air Resources Board (ARB) staff responsible for implementing U.S. EPA monitoring requirements and using the data in ozone data analyses

and health studies.

Urban Network Design Requirements

1. Considering the ozone minimum monitoring re quirements that are already promulgated through 40 CFR Part 58, is the considered change to these requirements sufficient to ensure a minimally adequate network in urban areas?

The requirement for one monitor to be placed in MSAs of population between 50,000 and less than 350,000 is clearly warranted in locations where th ere is the absence of a design value, primarily because of the large number of pe ople potentially affected by any standard

exceedances.

2. We are considering a timeline that would re quire newly required ozone monitors to be operational no later than January 1, 2011, based on the expectation that final rulemaking will be completed in 2009. Is this schedule appropriate or should EPA consider providing an additional year for new monitors to be deployed (or re located)? What would be the advantages or disadvantages of a stagger ed deployment schedule?

Based on the experience in California, 18 mont hs is adequate if funding is provided and implementation can be accomplished with existing staff. If funding and staff resources are not adequate, a staggered deployment schedule that extends over the following year should be considered. While attainment designations woul d be delayed by a year, this may not adversely affect control programs as any nonattainment areas with populations of this size are likely to be affected by ozone transport from larger, upwind c ities, and will already be receiving the benefit of control programs in these areas.

Non-Urban Network Design Requirements

1. We are considering a new requirement that each State operate a minimum of three nonurban ozone monitors to meet certa in objectives (described abo ve). Considering the stated objectives of the non-urban ozone monitoring requir ements, is three requir ed monitors per state sufficient?

The choice of three non-urban m onitors per state appears arbitr ary with no acknowledgement of geographic size differences, poten tial for transport from upwin d area or ozone severity. USEPA’s impressive ozone modeling capabilities could be used to identify broad geographic

areas where additional non-urban ozone monitoring is warranted.

2. What factors should be consider ed in the siting of ozone mon itors to assess impacts on ozone sensitive vegetation in na tional parks, wilderness areas, and other ecosystems?

15Factors that relate to the potenti al for higher ozone levels should be considered. These include proximity to upwind source regions, size of the source region, mixing ratio s recorded at upwind monitors, smaller potential for deposition losses (s horter transport distance s, transport over water bodies or areas with less vege tation), higher elevations (decoupl ed from night-time surface NO X sources), and sunnier areas with higher photolysis rates.

3. In addition to the objectives that have been described for non-urban ozone monitors, what other objectives should be consid ered in the final network desi gn? How would the consideration of additional objectives, if any, affect the minimum number of non-urban required monitors?

The resources available for equipment, shelters , operations and personnel should be considered. Non-urban ozone monitoring may be useful fo r ozone transport analyses and ozone model evaluation. Monitoring near ozone sensitive vegetation, especially areas where forest health or ecosystem monitoring is occurri ng, should be considered. I do not think these considerations should affect the minimum number of non-urban required monitors.

4. Current ozone monitoring regulations (described in Appendix E of 40 CFR part 58) include requirements for station and probe siting (e.g., ver tical distance of inle ts, set-back distances from roadways). Are these requirements (t hat have been developed for urban monitors) appropriate for non-urban ozone monitors? Wh at changes, if any, should be considered?

Yes, they are still applicable to maintain uniform siting crite ria throughout the entire network (urban and non-urban). Monitori ng at higher elevations with snow during the winter needs to be

seasonal to facilitate site access. More attention needs to be placed to setbacks from trees and other vegetation because of the potential for ozon e deposition. And to setbacks from roadways as there is unlikely to be co-located NO X monitoring to identify episodes of ozone titration.

5. We believe that States should have the opti on of designating that existing non-urban ozone monitors that are potentially operated by anot her agency (e.g., CASTNET monitors operated by the National Park Service) be utilized for meeting certain non-urban minimum monitoring requirements. What factors should States use to determine if such m onitors are appropriate to

include in their networks?

Other agencies would need to become part of their local Primary Quality Assurance Organization (PQAO) and follow uniform procedures, have staff take similar training, maintain same standard traceability, and submit data to USEPA’s Air Quality System (AQS).

Ozone Monitoring Season

1. We are considering changes to the required ozone monitoring seasons based on analyses of the patterns of ozone exceedances and occurrences of the Modera te level of the Air Quality Index, during periods outside of the currently re quired seasons. What other factors should be considered, if any, in the determination of the le ngth of the required monitoring season for each

State?

Provisions for high elevation sites with only seasonal access s hould be considered.

162. We believe that ozone monitors that are locate d at NCore stations should be operated on a year-round monitoring schedule. Under what circ umstances might it be a ppropriate to require year-round monitoring at other stations beside NCore?

The Health Effects Institute or other repr esentations of the ai r pollution epidemiology community should be consulted as to where yea r-round ozone measurements would be useful for epidemiologic cohort studies.

3. We are considering that change s to the required ozone monito ring season be applicable to existing monitors beginning in 2010, one year ahe ad of the deployment schedule for newly required ozone monitors. Is this sc hedule reasonable for existing monitors?

Yes, it is a reasonable schedule as the logistics are relativ ely straightforward.

17

### Dr. Delbert J. Eatough

The subject of this charge is not my area of expe rtise. I have responded only to those questions where I think I can give useful input.

Urban Network Design Requirements

1. Considering the ozone minimum monitoring re quirements that are already promulgated through 40 CFR Part 58, is the considered change to these requirements sufficient to ensure a minimally adequate network in urban areas?

The proposed changes seem reasonable and adequate. The existence of Class 1 monitors covers many non-urban areas already and the NCORE site activation will give a reasonable year round

data set.

2. We are considering a timeline that would re quire newly required ozone monitors to be operational no later than January 1, 2011, based on the expectation that final rulemaking will be completed in 2009. Is this schedule appropriate or should EPA consider providing an additional year for new monitors to be deployed (or re located)? What would be the advantages or disadvantages of a stagger ed deployment schedule?

If the final rulemaking is completed this year , increasing the deployment on a staggered basis, depending on the available data, to either two or three years (i.e., a one ye ar extension for some, identified lower probability sites) seems reasonable.

Non-Urban Network Design Requirements

1. We are considering a new requirement that each State operate a minimum of three non
urban ozone monitors to meet cer tain objectives (described a bove). Considering the stated objectives of the non-urban ozone monitoring requir ements, is three requir ed monitors per state sufficient?

The criteria for the three sites seems reasonable. The inclusion of a wilder ness site as one might be relaxed if such sites already exist in the st ate. What happens if a state has no unmonitored

MSA which models and other reasonable estimati ons indicates will be likely to exceed the 85%

value?

WY is certainly an outlier in the data set. Th e observation that the high ozone concentrations in WY appear to be associated with VOC emissi ons from oil and gas recovery during winter inversions has implications for other areas. I have made an additional comment on this below.

182. What factors should be considered in the siting of ozone monitors to assess impacts on ozone sensitive vegetation in national parks , wilderness areas, and other ecosystems?

3. In addition to the objectives that have been described for non-urban ozone monitors, what other objectives should be considered in the final network design? How would the consideration of additional objectives, if any, e ffect the minimum number of non-urban required monitors?

4. Current ozone monitoring regulations (described in Appendix E of 40 CFR part 58) include requirements for stati on and probe siting (e.g., vertical distance of inlets, set-back distances from roadways). Are these require ments (that have been developed for urban monitors) appropriate for non-urban ozone m onitors? What changes, if any, should be

considered?

5. We believe that States should have the option of designating that existing non-urban ozone monitors that are pot entially operated by another agency (e.g., CASTNET monitors operated by the National Park Servi ce) be utilized for m eeting certain non-urban minimum monitoring requirements. What factors should States use to determine if such monitors are appropriate to include in their networks?

Ozone Monitoring Season

1. We are considering changes to the required ozone monitoring seasons based on analyses of the patterns of ozone exceedances and occurrences of the Modera te level of the Air Quality Index, during periods outside of the currently re quired seasons. What other factors should be considered, if any, in the determination of the le ngth of the required monitoring season for each

State?

There is evidence that even at low Ozone concen trations, there is photo oxidation of material during the winter which leads to high PM levels during inversions in high mountain valleys. This is seen, for example, in our studies on th e composition and apportionme nt of PM in the Salt Lake City area during winter i nversions (Long et al., 2003, 2005) Identifying some of these regions for year round joint ozone monitoring and fine particulate specia tion would be useful.

Salt Lake is one such location. Boise could well be another. In cluding some PM studies in the WY region where high winter ozone ha s been observed could be useful.

2. We believe that ozone monitors that are locate d at NCore stations should be operated on a year-round monitoring schedule. Under what circum stances might it be a ppropriate to require year-round monitoring at other stations beside Ncore?

See response to 1 in this section.

3. We are considering that change s to the required ozone monito ring season be applicable to existing monitors beginning in 2010, one year ahe ad of the deployment schedule for newly required ozone monitors. Is this sche dule reasonable for existing monitors?

19Yes.

References:

Russell W. Long, Norman L. Eatough, Nolan F. Mangelson, Wesley Thompson, Kyle Fiet, Scott Smith, Rachel Smith, Delbert J. Eatough, C. Ar den Pope, William E. Wilson (2003). “The Measurement of PM2.5, Including Semi-Volatile Components, in the EMPACT Program: Results from the Salt Lake City Study and Implications for Public Awareness, Health Effects, and Control Strategies.” Atmospheric Environment, 37; 4407-4417.

Russell W. Long, William K. Modey, Phillip S. Sm ith, Rachel Smith, Cristina Merrill, Joshua Pratt, Andrew Stubbs, Norman L. Eatough, Delbert J. Eatough, William C. Malm, and William E. Wilson. (2005) “One- and Three-Hour PM 2.5 Characterization, Speciation, and Source Apportionment Using Continuous and Inte grated Samplers.” Aerosol Science and Technology, 39:238-248.

20

### Mr. Dirk Felton

Urban Network Design Requirements

1. Considering the ozone minimum monitoring re quirements that are already promulgated through 40 CFR Part 58, is the considered change to these requirements sufficient to ensure a minimally adequate network in urban areas?

The requirement to add monitors in MSAs as small as 50,000 may be burdensome to some monitoring agencies. One element that should be added to the regulation is the ability to waive the monitoring requirement if the State designa tes the MSA as non-attain ment. With the new lower NAAQS, the non-attainment areas in some st ates cover large areas and several MSAs. It is quite possible that upwind, rural or transport oriented monitors and monitors in adjacent MSAs can adequately justify th e determination of non-attainment fo r small MSAs without a monitor.

The RA should also have the discretion of waiv ing additional monitors th at either can’t meet siting requirements in certain urban areas or wher e the cost to install a monitor is excessive and out of the reach of the monitoring agency.

2. We are considering a timeline that would re quire newly required ozone monitors to be operational no later than January 1, 2011, based on the expectation that final rulemaking will be completed in 2009. Is this schedule appropriate or should EPA consider providing an additional year for new monitors to be deployed (or re located)? What would be the advantages or disadvantages of a stagger ed deployment schedule?

The schedule is appropriate only if monitoring agencies already have a suitable facility to install additional monitors. For these existing locati ons, the monitoring agencies will need calendar year 2010 to modify their network plan, to m odify budgets and to purchase and install new equipment. The timeline should establish a start date of 2012 for completely new installations. This extra year will be needed because monitori ng locations are very difficult to site in urban areas. In these areas, conventional monitoring shelters are usually e ither banned by building codes or can’t be sited properly due to the cost of property and the density of tall structures. In some of these situations, monito ring agencies have to go to th e expense of modifying existing buildings whether public or private to accommodate monitoring equipment.

Non-Urban Network Design Requirements

1. We are considering a new requirement that each State operate a minimum of three nonurban ozone monitors to meet certa in objectives (described abo ve). Considering the stated objectives of the non-urban ozone monitoring requir ements, is three requir ed monitors per state sufficient?

The plan to require three monitors per state is a bit too cookie cutter to adequately meet the monitoring needs in each state. Many states have multiple rural areas, some separated by mountains, that are distant from each other and are affected by sepa rate upwind sources. It is likely that the plan for three non-urban monitors will only be adequate for a few states. The EPA

21must be flexible and should encourage period ic discussions between OAQPS, the EPA Regional Offices, monitoring agencies and perhaps other st ake holders such as health researchers to

determine the minimum number and location of additional monitors.

2. What factors should be consider ed in the siting of ozone mon itors to assess impacts on ozone sensitive vegetation in na tional parks, wilderness areas, and other ecosystems?

The importance of altitude and local terrain is often overlook ed in monitor siting. Rural

monitors could be situated on a mo untain top, on an elevated platea u or in a deep valley. These

terrain features will affect local Ozone concentr ations and could detrimen tally reduce the scale of the monitor. Monitoring is expensive and rura l monitors should be si ted to represent large

scales.

3. In addition to the objectives that have been described for non-urban ozone monitors, what other objectives should be consid ered in the final network desi gn? How would the consideration of additional objectives, if any, effect the minimum number of non-urban required monitors?

Transport is another objective th at could be served by a suitably placed rural monitor. The installation of a transport monitor can be very important if it is used to help with attainment planning for downwind areas. The states that have non-attainme nt areas or whose emissions

contribute to non-attainment areas should be provided w ith the resources to establish monitoring

networks that exceed the mi nimum requirements.

4. Current ozone monitoring regulations (described in Appendix E of 40 CFR part 58) include requirements for station and probe siting (e.g., ver tical distance of inle ts, set-back distances from roadways). Are these requirements (t hat have been developed for urban monitors) appropriate for non-urban ozone monitors? Wh at changes, if any, should be considered?

The set-back distances from roads and other lo cal sources for non-urban, rural monitors should be increased to the extent possible. Rural m onitors should represent la rge spatial scales and influences such as NOx scavenging from n earby sources will alter the apparent Ozone concentration for the entire area represented by the monitor. Ideally, the monitor should be situated in a “typical” spot in the area to be represented by the new monitor. If the area is a nearly roadless Class 1 wilderness area, the mon itor should be quite far from a road. If the nonurban monitor is actually representing a suburban commuter area outside of a larger MSA then it is acceptable to be closer to a road way or other typical local sources.

5. We believe that States should have the opti on of designating that existing non-urban ozone monitors that are potentially operated by anot her agency (e.g., CASTNET monitors operated by the National Park Service) be utilized for meeting certain non-urban minimum monitoring requirements. What factors should States use to determine if such m onitors are appropriate to

include in their networks?

It has yet to be demonstrated that CASTNET can reliably meet the QA requirements that would make their data comparable to state and local monitoring networks. The CASTNET network is operated by a contractor who is selected through a competitive bidding process. It is possible

22that as the contract is awarded in future years to the same or another vendor, the data quality could vary.

State and local monitoring agenci es should carefully evaluate th e data quality of all of the monitors in their area. States should be perm itted to audit the operation of either CASTNET or NPS monitors that potentially could be includ ed as a component of a comprehensive state monitoring network.

Ozone Monitoring Season

1. We are considering changes to the required ozone monitoring seasons based on analyses of the patterns of ozone exceedances and occurrences of the Modera te level of the Air Quality Index, during periods outside of the currently re quired seasons. What other factors should be considered, if any, in the determination of the le ngth of the required monitoring season for each

State?

In states with cold winters, seasonal roads or high altitude monitoring locations, it may not be possible to initiate monitoring on the proposed ea rlier start dates at every location. The EPA should permit reasonably delayed start dates if acce ss to a monitoring location is prohibited or delayed due to snow or mud conditions.

Population exposure monitors should be given the highest priority for in itial startup at the beginning of the monitoring season. The EPA should consider not changing the monitoring season for the non-urban and ecosystem oriented monitors. The data from these sites is likely to be less valuable when air temperatures are st ill relatively cold and sensitive vegetation is dormant or snow covered. Monitoring agencies utilize the period in be tween monitoring seasons to perform instrument maintenance, re-certify calibrators and train staff. Permitting delayed start

dates for the non-urban monitors will also ease the difficulty of starting many monitors on the

same date.

2. We believe that ozone monitors that are locate d at NCore stations should be operated on a year-round monitoring schedule. Under what circ umstances might it be a ppropriate to require year-round monitoring at other stations beside NCore?

Due to the nature of NCore siting, most NCor e sites will not be located where the Ozone concentrations are the highest. It would be appr opriate to also monitor year round at one of the highest Ozone concentration sites for each non-attain ment area. This will provide context for the

NCore data.

3. We are considering that change s to the required ozone monito ring season be applicable to existing monitors beginning in 2010, one year ahe ad of the deployment schedule for newly required ozone monitors. Is this sc hedule reasonable for existing monitors?

A 2010 start date for a longer monitoring season for existing monitors would be acceptable if the regulation was finalized before th e end of the first Quarter of 2009.

23

### Dr. Phil K. Hopke

Urban Network Design Requirements

1. Considering the ozone minimum monitoring re quirements that are already promulgated through 40 CFR Part 58, is the considered change to these requirements sufficient to ensure a minimally adequate network in urban areas?

At least one monitor in each MS A with more than 50,000 is certainly warranted. I suggest a key

consideration here has to be that the concentration of ozone is also critically important in control of PM given the role of oxidants in the formation of secondary part icles. It is time we looked at the problem from a multiple pollutant perspective bot h in terms of the health effects and in terms of the control strategies. To do and fully protect public health requires that we have adequate measurements of all of the key pollutant s in any area of reasonable population.

I would second George Allen’s comment that we really should have a commercially available ethylene chemiluminescence monitor to use as a QA re ference. It does not ma ke a lot of sense to

have as the FRM as monitor that no one can actually buy and use.

2. We are considering a timeline that would re quire newly required ozone monitors to be operational no later than January 1, 2011, based on the expectation that final rulemaking will be completed in 2009. Is this schedule appropriate or should EPA consider providing an additional year for new monitors to be deployed (or re located)? What would be the advantages or disadvantages of a stagger ed deployment schedule?

At this point, state and local ag encies are hard pressed for fundi ng. At the same time, one would suggest that from a public health protection standpoint, it woul d be important to deploy the monitors as quickly as possible. However, there should be resources made available to the state, local, and tribal agencies to defray the costs of the redeployment or the acquisition of additional

monitors.

Non-Urban Network Design Requirements

1. We are considering a new requirement that each State operate a minimum of three nonurban ozone monitors to meet certa in objectives (described abo ve). Considering the stated objectives of the non-urban ozone monitoring requir ements, is three requir ed monitors per state sufficient?

We consider Montana and Rhode Island equivalent in the need of monitors per unit area? This is clearly a very strange idea. We can certainly ap ply appropriate models a nd look at the real needs to monitor and where they will need to be pla ced in order to meet the underlying objectives. Given the disparity in the si ze of states, the distribution of population centers and where transported ozone represents a significant regiona l control problem, this requirement appears arbitrary. There are a number of small eastern st ates where this would not appear very sensible and other states where it will clearly be inadequate . Who is to decide whether or not to exceed

24the minimum number? There needs to be a clear er definition of the criteria for siting the

monitors and that would define the minimum num ber per area. We have adequate modeling capabilities that can provide good in dications of the numbers of diffe rent ozone regions that exist

in a state. We can also think about monitors located in contiguous states to potentially serve to

cover an area as well. We need to be less fixate d by the number of monitors and more ties to the underlying motivations for the monitoring and our best understanding of the atmospheric processes to deploy limited resources to provide the most benefit.

2. What factors should be considered in the si ting of ozone monitors to assess impacts on ozone sensitive vegetation in na tional parks, wilderness areas, and other ecosystems?

We need to look at cumulative indices of exposure for the plants. We can estimate these exposures from appropriate modeling efforts and gi ven the nature of the ecosystem, estimate the likely damage. If we are really interested in pr otecting the vegetation, then it is worth the effort to customize the plans for each major area of the country having significantly different types of vegetation.

3. In addition to the objectives that have been described for non-urban ozone monitors, what other objectives should be consid ered in the final network desi gn? How would the consideration of additional objectives, if any, effect the minimum number of non-urban required monitors?

Clearly, a major concern for monitoring in rural areas is to provide critical data for model testing and validation. They also can provide some additional data for warning of pending ozone episodes in areas downwind of the monitor.

4. Current ozone monitoring regulations (described in Appendix E of 40 CFR part 58) include requirements for station and probe siting (e.g., ver tical distance of inle ts, set-back distances from roadways). Are these requirements (t hat have been developed for urban monitors) appropriate for non-urban ozone monitors? Wh at changes, if any, should be considered?

Even in rural areas, there could be significant NO sources and one would wa nt to site well away from such sources. We still want glass and Teflon inlets, etc.

5. We believe that States should have the opti on of designating that existing non-urban ozone monitors that are potentially operated by anot her agency (e.g., CASTNET monitors operated by the National Park Service) be utilized for meeting certain non-urban minimum monitoring requirements. What factors should States use to determine if such m onitors are appropriate to

include in their networks?

Clearly the monitoring locations have to meet the needs identified under question 2 above. The key issue is whether or not they can be operated with the same level of quality assurance as the SLAMS monitors. If so, fine.

25Ozone Monitoring Season

1. We are considering changes to the required ozone monitoring seasons based on analyses of the patterns of ozone exceedances and occurrences of the Modera te level of the Air Quality Index, during periods outside of the currently re quired seasons. What other factors should be considered, if any, in the determination of the le ngth of the required monitoring season for each

State?

Again, we need to think in multiple pollutant term s. Secondary aerosol is still formed in the winter. Exposures to ozone and other pollutants occur. We will never sort out the requirements to protect health from the exposure mixture th at the atmosphere produces without making year

round measurements. If the SLAMS site is mon itoring other pollutants, then the incremental cost of running that monitor all of the year is pretty minimal and well worth the extra effort and

expense.

2. We believe that ozone monitors that are locate d at NCore stations should be operated on a year-round monitoring schedule. Under what circ umstances might it be a ppropriate to require year-round monitoring at other stations beside NCore?

Again, one needs to look at the needs for unders tanding the behavior of the suite of pollutants and whether ozone data would pr ovide critical information need ed to make the management judgments needed to adequately protect public health.

3. We are considering that changes to the requi red ozone monitoring season be applicable to existing monitors beginning in 2010, one year ahe ad of the deployment schedule for newly required ozone monitors. Is this sc hedule reasonable for existing monitors?

It is not clear that it would be useful to do this uniformly across the countr y. It might make more sense to phase these into those areas that are mo st sensitive and where the data would prove most

useful.

26

### Dr. Rudolf Husar

Ozone Monitoring Season

1. We are considering changes to the required ozone monitoring seasons based on analyses of the patterns of ozone exceedances and occurrences of the Modera te level of the Air Quality Index, during periods outside of the currently re quired seasons. What other factors should be considered, if any, in the determination of the le ngth of the required monitoring season for each

State?

I think that mandating a month- by-month fine tuned monitoring season to each state is unnecessary. If such adjustments for the shoulder seas ons are in fact made, th e states that have a

short ozone season should be monitored less.

2. We believe that ozone monitors that are locate d at NCore stations should be operated on a year-round monitoring schedule. Under what circum stances might it be a ppropriate to require year-round monitoring at other stations beside NCore?

Regional/continental background sites and/or high elevation sites. These would document the spring stratospheric ozone, trans-continental (Asian) ozone transport and other larges-scale

processes.

3 . We are considering that c hanges to the required ozone monito ring season be applicable to existing monitors beginning in 2010, one year ahe ad of the deployment schedule for newly required ozone monitors. Is this sche dule reasonable for existing monitors?

No comment. It is a feasibility issue.

27

### Dr. Kazuhiko Ito

Urban Network Design Requirements

1. Considering the ozone minimum monitoring re quirements that are already promulgated through 40 CFR Part 58, is the considered change to these requirements sufficient to ensure a minimally adequate network in urban areas?

EPA may need to accommodate the concerns ex pressed by State air monitoring agencies and multi-state air planning organizations that these requirements ignore the needs that States and

localities have for additional monitors to meas ure ozone levels in areas with populations under 350,000. Judging from the figure in the white paper, it looks like there may be about 20 MSAs with less than 350,000 people that may be near the border of non-attainment.

2. We are considering a timeline that would re quire newly required ozone monitors to be operational no later than January 1, 2011, based on the expectation that final rulemaking will be completed in 2009. Is this schedule appropriate or should EPA consider providing an additional year for new monitors to be deployed (or re located)? What would be the advantages or disadvantages of a stagger ed deployment schedule?

It seems to me that there is no need to delay the deployment for the larger MSAs with existing sites even if setting up additional sites may take additional time, unless EPA needs to relocate some of the existing sites. I don’t see disadvantage of a staggere d deployment schedule if they

are necessary.

Non-Urban Network Design Requirements

1. We are considering a new requirement that each State operate a minimum of three nonurban ozone monitors to meet certa in objectives (described abo ve). Considering the stated objectives of the non-urban ozone monitoring requir ements, is three requir ed monitors per state sufficient?

There must be something like “Data Quality Objectives” (DQO) to determine whether or not some specific number of monitors is sufficient to achieve the goal. Without knowing the goal in some numerical manner, this question cannot be concretely answered. I suppose the following questions are more specific.

2. What factors should be considered in the si ting of ozone monitors to assess impacts on ozone sensitive vegetation in na tional parks, wilderness areas, and other ecosystems?

I am not familiar with the quantitative relationships (i.e., linear or non-linear?) between ozone and the effects on sensitive vegetations, but the siting of the monitors should consider: (1) the known quantitative relationship between ozone a nd the sensitive vegeta tion; (2) the spatial distribution of such vegetations; and, (3) prediction mode l of ozone concentra tions over the areas where sensitive vegetations exist. The siti ng should be done to minimize the uncertainty

28associated with the ozone prediction over the areas that are densely populated with such vegetations.

3. In addition to the objectives that have been described for non-urban ozone monitors, what other objectives should be consid ered in the final network desi gn? How would the consideration of additional objectives, if any, effect the minimum number of non-urban required monitors?

I don’t personally use them, but there are m odels (e.g., CMAQ) out th ere that predict air pollution levels including ozone. I imagine that prediction and model valid ation of these models rely on the locations of existing monitors. If EPA uses these models, why not also consider siting monitors where the model performance would improve.

4. Current ozone monitoring regulations (described in Appendix E of 40 CFR part 58) include requirements for station and probe siting (e.g., ver tical distance of inle ts, set-back distances from roadways). Are these requirements (t hat have been developed for urban monitors) appropriate for non-urban ozone monitors? Wh at changes, if any, should be considered?

I took a quick look at Appendix E of 40 CFR part 58. Regarding the probe height, it says: “The probe or at least 80 percent of the monitoring pa th must be located between 3 and 15 meters above ground level.” I am not sure if this hei ght requirement is appropriate in determining the exposure of sensitive vegetation. Perhaps it needs to be lower, but one needs to know the concentration gradient (profile) of ozone near the ground to take into consideration scavenging of ozone by the surface characteristic s including those of vegetations.

5. We believe that States should have the opti on of designating that existing non-urban ozone monitors that are potentially operated by anot her agency (e.g., CASTNET monitors operated by the National Park Service) be utilized for meeting certain non-urban minimum monitoring requirements. What factors should States use to determine if such m onitors are appropriate to

include in their networks?

I am not familiar with the difference in the proc edures, analytical methods, or siting requirements between the CASTNET monitors vs. EPA monitors, so I cannot provide specific comments, but if they are comparable, then any CASTNET monitors that meet requirements in Questions 2, 3,

and 4 above should be included.

Ozone Monitoring Season

1. We are considering changes to the required ozone monitoring seasons based on analyses of the patterns of ozone exceedances and occurrences of the Modera te level of the Air Quality Index, during periods outside of the currently re quired seasons. What other factors should be considered, if any, in the determination of the le ngth of the required monitoring season for each

State?

I am generally opposed to restricting the availabl e data for research purposes. If the change results in shorter sampling periods, such decision needs to take into consideration the balance between the possible information to be lost vs . the information gained by additional sampling

29locations (because you trade these two for a fixed budge t, I assume). It should be noted that, as far as the health effects are concerned, th e current NAAQS is NOT based on a clear-cut threshold below which we don’t observe any effect s. This means that, if we shutdown ozone monitoring for areas and periods we observe leve ls below the current standard, then we are eliminating the future data for research from whic h we will base our future standards! However, based on the EPA’s presentation during the conf erence call, the only one state would have a

shorter ozone season.

2. We believe that ozone monitors that are locate d at NCore stations should be operated on a year-round monitoring schedule. Under what circ umstances might it be a ppropriate to require year-round monitoring at other stations beside NCore?

If the spatial variation of ozone is not easily pr edicted in a MSA, additi onal year-round monitors may be needed to characterize such variations. Also, the seasonal cycles and the relationship between ozone and other pollutants must be differe nt from city to city or region to region.

Also, as far as air pollution ep idemiological studies are conc erned, I sense that the more emphasis will be placed in multi-pollutant eval uation. Then, the NAAQS will also have to emphasize multi-pollutant context. If this happ ens, then, the longer the ozone sampling period, the better for the multi-pollutant evaluation. Based on the EPA’s presentation during the conference call, many states would have longer oz one sampling seasons. I welcome this change.

3. We are considering that changes to the requi red ozone monitoring season be applicable to existing monitors beginning in 2010, one year ahe ad of the deployment schedule for newly required ozone monitors. Is this sc hedule reasonable for existing monitors?

I am not familiar with the operational aspect of changing (extending) the ozone monitoring season, but given that the monitors are conti nuous analyzers, I don’t imagine it would be unfeasible to do this for existing monito rs ahead of the de ployment schedule.

30

### Dr. Donna Kenski

Urban Network Design Requirements:

1. Considering the ozone minimum monitoring requirements that are already promulgated through 40 CFR Part 58, is the considered cha nge to these requirements sufficient to ensure a minimally adequate network in urban areas?

I support the proposed change to require mon itoring in MSAs of populations between 50,000 and 350,000, although I suggest that this requirement be tempered by an allowance to reduce monitoring if the data sh ow little or no potential for exceedin g the NAAQS. For example, if an area has a recent design value (withi n the last 5 years) less than 85% of the current NAAQS, the requirement for a new monitor could be waiv ed (as Table D-2 of 40CFR part 58 App. D currently permits). Similarly, after 3 years of monitoring in these new areas, a resulting design

value less than 85% of the standard should allow the states to rem ove or relocate the monitor in that area. The intent, as in Table D-2, is to characterize ozone concentrations in areas with significant population, but not insi st on permanent monitors in ar eas where the data demonstrate little evidence of health impacts. In a few locations, from the map given, it looks like there are existing monitors very near the MSAs. EPA might consider substituting those on a case-by-case basis, if a state can provide supporting evidence (e.g., modeling or previous monitoring) that a nearby existing monitor can provide data that is representative of the MSA.

2. We are considering a timeline that would require newly required ozone monitors to be operational no later than January 1, 2011, based on the expectation that final rulemaking will be completed in 2009. Is this sc hedule appropriate or should EPA consider providing an additional year for new monitors to be deployed (or relocated)? What would be the advantages or disadvantages of a staggered deployment schedule?

EPA should allow the states at le ast a 1 year period from the ti me of rulemaking to the required operation of monitors. The proposed timeline se ems adequate, assuming the states are allotted funding early in the process so they can make pur chases of new equipment with sufficient lead time. A staggered deployment schedule might be useful for those few states with a lot of new sites (Texas?) but most states with only 2 or 3 new monitors would probably find it more efficient to make these changes at the same time; staggering deployment would unnecessarily complicate the process. Of course, when you co mbine the required new urban monitors with the new non-urban monitors, the numbers start to add up for all the states, in which case staggering deployment starts to make more sense.

Non-Urban Network Design Requirements

1. We are considering a new requirement that each State operate a minimum of three nonurban ozone monitors to meet certain objectiv es (described above). Considering the stated objectives of the non-urban ozone monitoring requirements, is three required monitors per state sufficient?

31Certainly three is sufficient for most states, but surely too many for some (RI? CT? NJ?) and perhaps not enough for others. Can there be a mo re equitable distributio n based on area? Or better yet, could we distribute them based on where we know vegetation is sensitive, and

consider the non-urban monitors that we already have? It se ems somewhat heavy-handed to make a blanket requirement for every state rega rdless of size, existing monitors, and sensitive vegetation.

2. What factors should be considered in th e siting of ozone monitors to assess impacts on ozone sensitive vegetation in national parks, wilderness areas, and other ecosystems?

Expected concentration and the presence of sensitiv e species. One might want to consider the practical aspects like ease of access to the site, co llocated equipment, etc. But ozone has harmful effects on agricultural and ornamental vegetati on as well, so let’s no t restrict our ozone monitoring in nonurban areas to wilderness areas.

3. In addition to the objectives that have been described for non-urban ozone monitors, what other objectives should be considered in the final network design? How would the consideration of additional objectives, if any, e ffect the minimum number of non-urban required monitors?

This network really ought to consider geograp hic distribution without trying to parse equal

numbers of monitors to each state. Plot the existing nonur ban monitors (including state monitors, CASTNET and IMPROVE), find the hol es, and add enough monito rs to fill in the gaps. Terrain and likelihood of hi gher concentrations could also be factored in (we probably don’t need as many monitors in North Dakota as in Texas). Th ere’s nothing inherently wrong with using some carefully modeled ozone data to estimate where highest concentrations in currently unmonitored areas might be.

4. Current ozone monitoring regulations (described in Appendix E of 40 CFR part 58) include requirements for stati on and probe siting (e.g., vertical distance of inlets, set-back distances from roadways). Are these require ments (that have been developed for urban monitors) appropriate for non-urban ozone m onitors? What changes, if any, should be

considered?

These non-urban monitors might be sited more like the IMPROVE monitors with respect to distance from any potential sources.

5. We believe that States should have the option of designating that existing non-urban ozone monitors that are pot entially operated by another agency (e.g., CASTNET monitors operated by the National Park Servi ce) be utilized for m eeting certain non-urban minimum monitoring requirements. What factors should States use to determine if such monitors are appropriate to include in their networks?

These other network monitors should absolute ly be considered in developing a non-urban network, and efforts toward harmonizing the various networks should continue. The presence of stable, long-term funding is probably the most important factor to consider, followed closely

32by an adequate quality assurance program and some kind of network intercomparison to ensure reliable, comparable data with the other state monitors.

Ozone Monitoring Season

1. We are considering change s to the required ozone monito ring seasons based on analyses of the patterns of ozone exceedances and occurre nces of the Moderate level of the Air Quality Index, during periods outside of the currently required seasons. What other factors should be considered, if any, in the determination of the length of the required monitoring season for each State?

Thank you for posting the additional information on the Camalier ozone season analysis. It seems to be a reasonable approach and I concur with the conclusion to increase ozone season in a number of states. Another appro ach, or factor to examine, is to look at the timing of exceedances or values >0.06 ppm throughout the y ear and statistically predict how likely those concentrations might occur before the start of the monitoring se ason. That is, if Wisconsin has recorded an ozone concentration of 0.076 as early as April 20 in the past, how are likely is it that a similar concentration might occur 6 days earlier, before the official season begins? The work of Rasmus Benestad in predicting extreme events seems like a promising approach (Benestad, R., EOS, Trans. AGU 89:41, 7 Oct 2008).

2. We believe that ozone monitors that are loca ted at NCore stations should be operated on a year-round monitoring schedule. Under what circumstances might it be appropriate to require year-round monitoring at other stations beside NCore?

EPA should encourage, but not require, year-round monitoring at ozone sites. The NCore sites will provide a sufficient base of year-round mon itoring and will include the collocated species that make it more useful for health and chemistry studies. Of course more data is always better, but it comes at a cost. At this point, I don’t th ink there is sufficient a dded value to expanding the pool of year-round monitors (i.e., requiring all sites to monitor year-round) to justify the

additional cost. If future health data demonstr ate a pressing need for winter ozone data from additional sites, we could revis it this, but right now I don’t think the need is there.

3. We are considering that c hanges to the required ozone monito ring season be applicable to existing monitors beginning in 2010, one year ahead of the deployment schedule for newly required ozone monitors. Is this schedule reasonable for existing monitors?

Yes.

33

### Dr. Thomas Lumley

Urban Network Design Requirements

1. Considering the ozone minimum monitoring re quirements that are already promulgated through 40 CFR Part 58, is the considered change to these requirements sufficient to ensure a minimally adequate network in urban areas?

The addition of monitors in lo wer-population areas is an import ant step in ensuring that the NAAQS protect the US population. I believe the current density of monitors in larger urban areas is sufficient if they are appropriately loca ted in places where high er ozone concentrations are expected. A useful way to confirm this w ould be to summarize how many excedances of the proposed threshold in large urban areas were detected by only a single monitor

2. We are considering a timeline that would re quire newly required ozone monitors to be operational no later than January 1, 2011, based on the expectation that final rulemaking will be completed in 2009. Is this schedule appropriate or should EPA consider providing an additional year for new monitors to be deployed (or re located)? What would be the advantages or disadvantages of a stagger ed deployment schedule?

I have no relevant expertise on the feasibility of deploying monitors by 1/2011. If this schedule is feasible then postponing the deployment will significantly reduce the amount of data available in smaller urban areas by the ne xt revision of the standards. My non-expert reading of economic forecasts suggests that state budgets are likely to still be strained by th e current recession in 2010, so later deployment may be helpful for cost reasons.

Non-Urban Network Design Requirements

1. We are considering a new requirement that each State operate a minimum of three nonurban ozone monitors to meet certa in objectives (described abo ve). Considering the stated objectives of the non-urban ozone monitoring requir ements, is three requir ed monitors per state sufficient?

It is not clear to me that the number of monito rs in each state should be the same. States may differ greatly both in the amount of publically si gnificant ozone-sensitiv e vegetation and in the likelihood of high ozone levels. It seems more a ppropriate to customize the requirements to the

actual risks.

2. What factors should be consider ed in the siting of ozone mon itors to assess impacts on ozone sensitive vegetation in na tional parks, wilderness areas, and other ecosystems?

The likelihood of adversely high ozone concentrations; the sensitivity of the vegetation; the importance of the vegetation ecologically, as a public attraction, and as part of a more-or-less pristine wilderness area. In pa rticular, since vegetation (unlikel y human health) can safely be

34assumed to be unaffected by natural background levels of ozone, monitoring should focus on areas where anthropogenic ozone impacts ar e likely to cause vegetation damage.

3. In addition to the objectives that have been described for non-urban ozone monitors, what other objectives should be consid ered in the final network desi gn? How would the consideration of additional objectives, if any, affect the minimum number of non-urban required monitors?

I have no suggestions on this issue.

4. Current ozone monitoring regulations (described in Appendix E of 40 CFR part 58) include requirements for station and probe siting (e.g., ver tical distance of inle ts, set-back distances from roadways). Are these requirements (t hat have been developed for urban monitors) appropriate for non-urban ozone monitors? Wh at changes, if any, should be considered?

Increasing required distances from roads may be appropriate. In an ur ban setting there are constraints on required distance from roads that are not present in non-urban areas. In addition, important ozone-sensitive vegetati on is likely to live further fro m main roads than the typical member of the urban population.

5. We believe that States should have the opti on of designating that existing non-urban ozone monitors that are potentially operated by anot her agency (e.g., CASTNET monitors operated by the National Park Service) be utilized for meeting certain non-urban minimum monitoring requirements. What factors should States use to determine if such m onitors are appropriate to

include in their networks?

This seems appropriate. The monitors shoul d be operated on the same schedule and have accuracy comparable to the urban monitors, and they should be sited so as to capture the potential ozone impacts that th e standards protect against.

Ozone Monitoring Season

1. We are considering changes to the required ozone monitoring seasons based on analyses of the patterns of ozone exceedances and occurrences of the Modera te level of the Air Quality Index, during periods outside of the currently re quired seasons. What other factors should be considered, if any, in the determination of the le ngth of the required monitoring season for each

State?

I can’t think of any.

2. We believe that ozone monitors that are locate d at NCore stations should be operated on a year-round monitoring schedule. Under what circ umstances might it be a ppropriate to require year-round monitoring at other stations beside NCore?

Year-round monitoring at NCore st ations plus extension of th e monitoring season to capture

`Moderate’ ozone levels at other stations seems sufficient.

353. We are considering that change s to the required ozone monito ring season be applicable to existing monitors beginning in 2010, one year ahe ad of the deployment schedule for newly required ozone monitors. Is this schedule reasonable.

I have no relevant expertise on this issue.

36

### Dr. Peter H. McMurry

Urban Network Design Requirements

1. Considering the ozone minimum monitoring re quirements that are already promulgated through 40 CFR Part 58, is the considered change to these requirements sufficient to ensure a minimally adequate network in urban areas?

Based on my reading of the document and comments from other committee members who are more knowledgeable than I on this to pic, it seems reasonable to me.

2. We are considering a timeline that would re quire newly required ozone monitors to be operational no later than January 1, 2011, based on the expectation that final rulemaking will be completed in 2009. Is this schedule appropriate or should EPA consider providing an additional year for new monitors to be deployed (or re located)? What would be the advantages or disadvantages of a stagger ed deployment schedule?

It is my understanding that the new ozone monitors would need to be operational at the beginning of the 2011 ozone monitoring season, not necessarily on January 1. This seems reasonable. Committee members pointed that give n states’ current financial difficulties, some flexibility may be advisable. I am sympathetic to this concern.

Non-Urban Network Design Requirements

1. We are considering a new requirement that each State operate a minimum of three nonurban ozone monitors to meet certa in objectives (described abo ve). Considering the stated objectives of the non-urban ozone monitoring requir ements, is three requir ed monitors per state sufficient?

I am among the group of Committee members who ar e perplexed by this specification. I agree

with others that the focus needs to be on achie ving adequate coverage. After studying Figure 1 I was only able to find one state (Montana) that cu rrently has fewer than three sites (I recognize there may be other states whose sites do not meet the constraints defined by this proposal.)

2. What factors should be consider ed in the siting of ozone mon itors to assess impacts on ozone sensitive vegetation in na tional parks, wilderness areas, and other ecosystems?

Ozone may be a sentinel for climate change in some remote areas. Temperature changes will lead to changes in rainfall a nd vegetation. Biogenic emissions of compounds that react to produce ozone will be affected by those changes. Oz one concentrations might also be affected by temperature, which affects rates of reactions that produce ozone. If these processes were to affect ozone concentrations, long periods (years) of continuous monitoring (not only during the ozone NAAQS season) would be required to detect them. I am not expert on this topic, but certainly others are. I recognize th at this is not a topic that falls within the primary ozone NAAQS, but it

should be a consideration.

373. In addition to the objectives that have been described for non-urban ozone monitors, what other objectives should be consid ered in the final network desi gn? How would the consideration of additional objectives, if any, effect the minimum number of non-urban required monitors?

4. Current ozone monitoring regulations (described in Appendix E of 40 CFR part 58) include requirements for station and probe siting (e.g., ver tical distance of inle ts, set-back distances from roadways). Are these requirements (t hat have been developed for urban monitors) appropriate for non-urban ozone monitors? Wh at changes, if any, should be considered?

5. We believe that States should have the opti on of designating that existing non-urban ozone monitors that are potentially operated by anot her agency (e.g., CASTNET monitors operated by the National Park Service) be utilized for meeting certain non-urban minimum monitoring requirements. What factors should States use to determine if such m onitors are appropriate to

include in their networks?

Wherever possible, an effort should be made to qualify ozone monitors in other networks (CASTNET, NPS, etc) as FRM monitors. Also, oz one monitors should be located at sites where other species are also being measured.

Ozone Monitoring Season

1. We are considering changes to the required ozone monitoring seasons based on analyses of the patterns of ozone exceedances and occurrences of the Modera te level of the Air Quality Index, during periods outside of the currently re quired seasons. What other factors should be considered, if any, in the determination of the le ngth of the required monitoring season for each

State?

The clear message needs to be communicated to stat es that there is substantial value in operating ozone monitors year round, not only during th e primary NAAQS ozone monitoring season. The potential value of such measurements in suppo rting model evaluation, assessing climate change impacts, etc., should be communicated so that states are aware of the benefits.

2. We believe that ozone monitors that are locate d at NCore stations should be operated on a year-round monitoring schedule. Under what circ umstances might it be a ppropriate to require year-round monitoring at other stations beside NCore?

There are compelling arguments for making year-r ound measurements wherever possible. These include (1) the possibility that instruments operate better when they are operated continuously, (2) the possibility that data can be used for many purposes other than meeting NAAQS requirements. EPA should communicate to state agencies the ways in which continuous ozone

data could be of value. These include model evaluation, assessment of climate change on ozone concentrations, assessment of unanticipated impacts of new sources (e.g., emissions from Wyoming’s energy industry), assessment of multi- pollutant health impact s when ozone is below NAAQS levels, etc. It should be emphasized that there is no known lower threshold for ozone

health effects.

383. We are considering that change s to the required ozone monito ring season be applicable to existing monitors beginning in 2010, one year ahe ad of the deployment schedule for newly required ozone monitors. Is this sc hedule reasonable for existing monitors?

I defer.

39

### Mr. Richard L. Poirot

Urban Network Design Requirements

1. Considering the ozone minimum monitoring requirements that are already promulgated through 40 CFR Part 58, is the considered change to these requirements sufficient to ensure a minimally adequate network in urban areas?

The proposed change is probably “sufficient” to ensure a minimally adequate network in urban areas, and the “logic” of affording “protection” to populations in smaller MSAs is reasonable. However, population levels – especially for c ities as small as 50,000 – may not be the best predictor of (currently unmon itored) locations where exceedan ces of the new NAAQS are most likely, nor is a new monitor necessarily the best means to afford “protection” to a given population. Considering that the primary and secondary NAAQS are the same, and given the “suburban” nature of many existing monitoring site s, it can also become difficult to distinguish between urban and rural monitoring sites and objec tives, and it might be more useful to think

more in terms of an urban/rural continuum ra ther than separate networks with separate objectives.

Rather than deploying new monitoring “urban” sites strictly accord ing to a MSA populationbased formula, other desirable monitoring obj ectives that might be considered include:

• Minimize spatial interpolation errors and un certainties – both for real-time mapping and for estimating longer-term exposure metrics for both health and se nsitive vegetation,

• Improve forecasting ability (are there key locations - or kinds of locations - that the forecasters would like to see to help improve their forecast accuracy?),

• Evaluate/improve forecast (or SIP backcast) mode ls (local, regional, continental, global),

• Evaluate/improve satellite estimates,

• Enhance consideration of multi-pollutant exposures and effects (and atmospheric chemistry) through collocation with other pollutant & meteorological measurements,

• Provide better indication of ‘true’ human exposure levels in inner city locations,

• Evaluate effects of control strategies or of projected population or industrial growth,

• Improve estimates of regional, transboundary an d transcontinental tran sport, as well as regional and “policy-relevant ” background concentrations.

For these reasons, EPA and the states should be enc ouraged to exercise subs tantial flexibility in implementing the new “urban” monitoring requiremen ts. For example, I strongly endorse Dirk’s suggestion to wave monitoring requirements fo r smaller MSAs which the state has designated

nonattainment.

2. We are considering a timeline that would require newly required ozone monitors to be operational no later than January 1, 2011, based on the expectation that final rulemaking will be completed in 2009. Is this schedule appropriate or should EPA consider providing an additional year for new monitors to be deployed (or re located)? What would be the advantages or disadvantages of a stagger ed deployment schedule?

40States are currently under severe bud getary constraints. Given this and the difficulty that can be associated with establishing new monitoring site s in urban areas (as opposed to adding ozone monitors at existing monitoring sites), a 1/1/ 11 deadline may be overly ambitious. A phased schedule that provides more time is likely to result in better data quality in the long-term, especially if new site locati ons need to be established.

Non-Urban Network Design Requirements

1. We are considering a new requirement that each State operate a minimum of three nonurban ozone monitors to meet certain obj ectives (described above). Considering the stated objectives of the non-urban ozone monitoring requ irements, is three required monitors pe r state sufficient?

While 3/state is an arbitrary proposal, the number generally seems about right given your stated multiple objectives (and/or is difficult to judge without knowing which existing “non-urban” sites may meet these criteria). In addition to the stated monitoring objectives, some of the additional objectives listed above for “urban” mon itoring might also be considered in selecting

new “rural” sites.

Sites at higher (relative) el evation can be especially valu able for evaluating transport contributions and model performance, but in many regions will also tend to measure higher

concentrations. So some states may be reluctant to sample at such locations without specific incentives or perhaps special designation as “research site s” not subject to compliance

determinations.

2. What factors should be considered in the si ting of ozone monitors to assess impacts on ozone sensitive vegetation in na tional parks, wilderness areas, and other ecosystems?

As always, substantial value is added if ozone measuremen ts are collocated with other measurements, and so adding ozone at IMPROVE sites would provide useful new information.

It can also be noted that EPA research on effect s of ozone on sensitive vegetation has been quite limited in recent years (decades), and so it could be valuable for EPA to form partnerships with Agencies like NPS, Forest Service and with academic groups to better coordinate monitoring and effects research activities. See for example th e NPS “Ozone Risk Assessment for Vital Signs

Networks” http://www.nature.nps.gov/air/Perm its/ARIS/networks/ozoneRisk.cfm

Some emphasis might also be placed on monitori ng (and/or effects resear ch) in locations with high densities of ozone-sensitive plants or where ozone effect s have been observed (such as foliar injury in FHA surveys), but where curre nt ozone standards are not expected to be exceeded. Also, given CASAC r ecommendations in the last 2 ozone NAAQS reviews to adopt a more biologically relevant cumulative seasonal secondary sta ndard, some emphasis might be placed on the kinds of locations where a SUM06 or W126 metric would be high relative to the 8- hour daily maximum.

3. In addition to the objectives that have been described for non-urban ozone monitors, what other objectives should be consider ed in the final network design?

41How would the consideration of additional obje ctives, if any, effect th e minimum number of nonurban required monitors?

See answers to previous questi ons. In addition, final decision s on the numbers of required new sites need to be balanced with considerations of alternate monitoring prio rities – such as longer monitoring seasons.

4. Current ozone monitoring regulations (described in Appendix E of 40 CFR part 58) include requirements for station and probe siting (e.g., ver tical distance of inle ts, set-back distances from roadways). Are these requirements (that have been developed for urban monitors) appropriate for non-urban ozone monitors? Wh at changes, if any, should be considered?

Given the blurred distinctions be tween urban and rural sites (& monitoring objectives), and for reasons of consistency, I think station and probe siting requirements should generally be the

same for rural and urban monitors

5. We believe that States should have the op tion of designating that existing non-urban ozone monitors that are potentially operated by anot her agency (e.g., CASTNET monitors operated by the National Park Service) be utilized for meeting certain non-urban minimum monitoring requirements. What factors should States use to determine if such mon itors are appropriate to

include in their networks?

Monitors not operated by State Agencies should be subject to the same QA/QC requirements imposed on state-operated sites.

Ozone Monitoring Season

1. We are considering changes to the required ozone monitoring seasons based on analyses of the patterns of ozone exceedances and occurrences of the Modera te level of the Air Quality Index, during periods outside of the currently re quired seasons. What other factors should be considered, if any, in the determination of the le ngth of the required monitoring season for each

State?

The various anomalies in the page 20 map of pr oposed ozone season requirements by state look a little silly from a science perspe ctive, and for various reasons, it might make more sense to require (or provide some incentives for) year-round sampling at some sites in all states. It would be useful to develop some estimates of the in cremental costs of extending the ozone monitoring season – especially at sites where other monitoring demands year-round attention. I would think the incremental cost of running year-round at such sites would be relatively small (and there can also be problems & costs associated with shut -down/start-up operations). Additional data from these sites would also have the added value of providing useful information on multi-pollutant exposures and effects and on atmospheric chemis try. I think there’s still much we don’t understand about the (multiple) cau ses for the general springti me maxima, intercontinental transport, winter photochemistr y, stratospheric intrusion, etc.

422. We believe that ozone monitors that are loca ted at NCore stations should be operated on a year-round monitoring schedule. Under what circum stances might it be a ppropriate to require year-round monitoring at other stations beside NCore?

I would think many of the NCore s ites might not be sited to meas ure peak ozone levels (in any season – but especially) in cooler months, and/or might not be ideally sited to help indicate broad spatial patterns. Possibly it would be useful to re quire at least 1 rural site per state for year-round sampling. Also, it seems likely that the site char acteristics to record maximum concentrations may be different in warm & cool seasons. For example, higher elevation / ridge top or “near water” sites often see highest c oncentrations in summer, while in -land valley locations might see higher concentrations in winter.

3. We are considering that c hanges to the required ozone monito ring season be applicable to existing monitors beginning in 2010, one year ahe ad of the deployment schedule for newly required ozone monitors. Is this sche dule reasonable for existing monitors?

This seems reasonable in most cases. Some rural sites – especially at hi gher elevation – can be

inaccessible in winter. Allowances should be made for such sites (which are also not likely to record the highest concentra tions in cooler months).

43

### Dr. Armistead Russell

Urban Network

1. Considering the ozone minimum monitoring re quirements that are already promulgated through 40 CFR Part 58, is the considered change to these requirements sufficient to ensure a minimally adequate network in urban areas?

2. We are considering a timeline that would require newly required ozone monitors to be operational no later than January 1, 2011, based on the expectation that final rulemaking will be completed in 2009. Is this schedule appropriate or should EPA consider providing an additional year for new monitors to be deployed (or re located)? What would be the advantages or disadvantages of a stagger ed deployment schedule?

I would not be overly aggressive in setting a schedule. First, I w ould ask the question as to what objective a specific cite addresses. Next, I would ask if the siting, and system could benefit from more thought than is allowed w ith the given schedule. Overa ll, I would argue for thoughtful flexibility.

Non-Urban Network

1. We are considering a new requirement that each State operate a mi nimum of three non-urban ozone monitors to meet certain objectives (descr ibed above). Considering the stated objectives of the non-urban ozone monitoring requirements, is three required monitors per state sufficient?

My first reaction to this re quirement was quite negative un til reading about the proposed flexibility, and even that may not be enough. Given the large variety of resources that inform us about ozone across the US, I am not sure that we need three non-urba n monitors in each state. I would look at the various available products (s atellite data, annual modeling simulations, nonroutine monitoring results (includi ng special study monitors), th e size of the state, population, etc., and use these to determine how many and wh ere the monitors should go. As stated above, I would argue for thoughtful flexibility.

2. What factors should be considered in the si ting of ozone monitors to assess impacts on ozone sensitive vegetation in na tional parks, wilderness areas, and other ecosystems?

My view is that the agency, along with the states, should look at where information is critically missing. Use the modeling results (of more than just ozone), statisti cal analysis, sate llite data (of more than just ozone) and current monitoring results to figure out where adding an ozone monitor to the network, preferably at a pre-existing (likely PM) m onitoring site. I would hesitate to site any new ozone monitor where there is not some other monitor already. The information typically is not as valuable as it would be if information on more pollutants is available at the

same site.

443. In addition to the objectives that have b een described for non-urban ozone monitors, what other objectives should be consid ered in the final network desi gn? How would the consideration of additional objectives, if any, effect the minimum number of non-urban required monitors?

I would be less worried about the modeling end (a s a modeler)... we make too little use of the

ones we have.

4. Current ozone monitoring regulations (descr ibed in Appendix E of 40 CFR part 58) include requirements for station and probe siting (e.g., ver tical distance of inle ts, set-back distances from roadways). Are these requirements (t hat have been developed for urban monitors) appropriate for non-urban ozone monitors? Wh at changes, if any, should be considered?

5. We believe that States should have the opt ion of designating that existing non-urban ozone monitors that are potentially operated by anot her agency (e.g., CASTNET monitors operated by the National Park Service) be utilized for meeting certain non-urban minimum monitoring requirements. What factors should States use to determine if such m onitors are appropriate to

include in their networks?

Ozone Monitoring Season

1. We are considering changes to the required ozone monitoring seasons based on analyses of the patterns of ozone exceedances and occurrences of the Modera te level of the Air Quality Index, during periods outside of the currently re quired seasons. What other factors should be considered, if any, in the determination of the le ngth of the required monitoring season for each

State?

Every city (> 350,000) should have at least one monitor going and reportin g all year round. In regards to other monitors,

2. We believe that ozone monito rs that are located at NCore stations should be operated on a year-round monitoring schedule. Under what circ umstances might it be a ppropriate to require year-round monitoring at other stations beside NCore?

3. We are considering that changes to the re quired ozone monitoring season be applicable to existing monitors beginning in 2010, one year ahe ad of the deployment schedule for newly required ozone monitors. Is this sc hedule reasonable fo r existing monitors ?

Yes.

45

### Dr. Jay R. Turner

Urban Network Design Requirements

1. Considering the ozone minimum monitoring requirements that are already promulgated through 40 CFR Part 58, is the considered change to these requirements sufficient to ensure a minimally adequate network in urban areas?

Monitoring should be conducted in all MSAs below 350,000 population to at least establish ozone air quality conditions. This is important given the role of ozone monitoring not only for NAAQS compliance determinations but also for AQI reporting. There should be flexibility in the timeline to deploy new monitors in such areas a nd the requirements to maintain monitoring in these smaller MSAs depending on the observed ozone levels.

2. We are considering a timeline that would require newly required ozone monitors to be operational no later than January 1, 2011, based on the expectation that final rulemaking will be completed in 2009. Is this schedule appropriate or should EPA consider providing an additional year for new monitors to be deployed (or re located)? What would be the advantages or disadvantages of a staggered deployment schedule?

What three-year period will be used for th e first round of designations under the May 2008 NAAQS revisions? If the ne w data are expected to inform the decision-making on nonattainment area boundaries, then every effort should be made to get these monitors operating

on a schedule consistent with the designation process. This might be particularly important for monitors being sited near the fr inge areas of existing nonattainment areas or monitors being sited in smaller MSAs in counties near, but curren tly outside, existing nona ttainment areas. MSAs smaller than 350,000 population and currently wit hout ozone monitoring c ould have staggered implementation to provide the monitoring agencies with flexibility in allocation of resources (it would be shame to buy ozone monitors for each of smaller MSAs only to find that sustained monitoring in many such areas would not be a pr iority) and mindful of the additional burden on personnel to establish and operate these new sites.

Non-Urban Network Design Requirements

1. We are considering a new requirement th at each State operate a minimum of three nonurban ozone monitors to meet certain objectives (described above). Considering the stated objectives of the non-urban ozone monitoring requir ements, is three requir ed monitors per state sufficient?

With the pattern towards ratcheting down the ozone standard, I am concerned about the low density of non-urban monitoring downwind of (generally large) urban ozone nonattainment areas, especially in the Midwestern United States. It is not clear to me that we are capturing the spatial extent of the ozone impact in such cas es. For example, a larg ely rural county at the downwind edge of a nonattainment area (but perhaps still within the MSA) might have the highest ozone design value; in this case, it shou ld be determined whether the plume is causing

46NAAQS violations further downw ind. While these areas might ha ve relatively low population, people living in these areas are impacted. (I re spect the philosophical issu es this might create with respect to a given urban area’s impact on ai r quality in the immedi ate downwind counties in light of larger scale, regional transport and the complexities in attributing observed burdens to emission source regions, but the urban plume patterns should be a considerat ion at least in areas with geographically isolated nonattainment areas.) Given this nee d, together with the need for monitoring with respect to obj ectives relevant to the sec ondary standard, three non-urban monitors per state might be sufficient in some but not all cases.

2. What factors should be considered in th e siting of ozone monitors to assess impacts on ozone sensitive vegetation in national parks , wilderness areas, and other ecosystems?

Existing estimates of ozone concen tration fields should be used to prioritize areas. States should be allowed to capitalize on existing monitoring conducted by other networks (e.g. CASTNET) to fulfill this monitoring objective.

3. In addition to the objectives that have been described for non-urban ozone monitors, what other objectives should be consid ered in the final network desi gn? How would the consideration of additional objectives, if any, effect the minimum number of non-urban required monitors?

See #1 above, which encourages placing addi tional emphasis on non-urban areas downwind of large urban ozone nonattainment areas.

4. Current ozone monitoring regulations (described in Appendix E of 40 CFR part 58) include requirements for station and probe siting (e.g., ver tical distance of inle ts, set-back distances from roadways). Are these requirements (that have been developed for urban monitors) appropriate for non-urban ozone monitors? Wh at changes, if any, should be considered?

No comments at this time.

5. We believe that States should have the op tion of designating that existing non-urban ozone monitors that are potentially operated by anot her agency (e.g., CASTNET monitors operated by the National Park Service) be utilized for meeting certain non-urban minimum monitoring requirements. What factors should States use to determine if such mon itors are appropriate to

include in their networks?

See #2 above; States should determine whether existing non-urban ozone monitors that are potentially operated by another agency are in loca tions consistent with th eir prioritized list of

sites based on estimated ozone levels. The da ily maximum 8-hour average might not be best ozone metric for prioritizing such areas and ot her metrics should be considered (e.g. reflecting upon analyses and considerations for the secondar y standard that were part of the mostrecent ozone NAAQS review process).

47Ozone Monitoring Season

1. We are considering changes to the required ozone monitoring seasons based on analyses of the patterns of ozone exceedances and occurrences of the Modera te level of the Air Quality Index, during periods outside of the currently re quired seasons. What other factors should be considered, if any, in the determination of the le ngth of the required monitoring season for each

State?

The analysis used to support adjustments to the state-specific ozone seasons seems reasonable

.

2. We believe that ozone monitors that are locate d at NCore stations should be operated on a year-round monitoring schedule. Under what circ umstances might it be a ppropriate to require year-round monitoring at other stations beside NCore?

Ozone monitors at NCore sites should be opera ted year-round. Many data analyses, including but

not limited to health effects st udies (including studies which mi ght not be focused on ozone but include it as a possible confounder), would benefit from year-round da ta. Also, ozone data can be useful when validating performance of certain por tions of chemical transport models that might be run for purposes other than ozone (e.g. fine PM).

3. We are considering that change s to the required ozone monito ring season be applicable to existing monitors beginning in 2010, one year ahe ad of the deployment schedule for newly required ozone monitors. Is this sc hedule reasonable for existing monitors?

What three-year period will be used for th e first round of designations under the May 2008 NAAQS revisions? This informati on is important when consideri ng the timelines for phasing in changes to the monitoring season.

48

### Dr. Warren H. White

Ozone monitoring season – general comments

An indication of the incrementa l cost of extending an existing seasonal site to year-round operation is missing from the materials provided for discussion. The AAMMS does not need to know the actual dollars involved, but does need an approximate “exchange rate” between 12- month operation and, say, 8-month operation. What are typical marginal costs as a fraction of

fixed costs?

I appreciate that a lot of e xperience and history has gone into the map of ozone monitoring seasons, but does it really have to be so comple x and spatially resolved? Wyoming, for example, scheduled to start monitoring year-round, is enti rely surrounded by states still scheduled to hibernate every winter. Is th ere any scientific rationale fo r creating this island defined by political rather than climatolog ical or topographical boundaries? Note that Schnell et al. (2009) “suggest that similar ozone produc tion [to that observed in Wyoming] during wintertime is probably occurring around the world under comp arable industrial and meteorological conditions.” I would prefer a uniform monito ring season everywhere, if only on aesthetic grounds, and would prefer it to be as long as we can afford, year -round if possible.

I don’t feel strongly about extending the monito ring season at ozone-only sites, where nothing else is measured, because we wouldn’t know how to interpret the resulting cold-weather data as an indication of other photochemical products and th eir aggregate effect on health and welfare. The NAAQS is set for ozone as “the indicator for a mix of O 3 and other photochemical oxidants” (Arnold et al., 2007), and the composition of the wi nter mix may differ from that of the summer

mix on which most current eviden ce for ozone-related health effect s is based. The presence of monitors for other variables should discourage shutting down a monitor for ozone.

References:

J. Arnold, Q. Meng, J. Pinto and W. Wilson (2007) Atmospheric chemistry and physics used in Integrated Science Assessments. Presente d to the Human Health Risk Assessment

subcommittee of the Board of Sc ientific Counselors, Bethesda, http://www.epa.gov/OSP/bosc/pdf/hhraltg3abstracts.pdf

. R.C. Schnell, S.J. Oltmans, R.R. Neely, M.S. E ndres, J.V. Molenar and A.B. White (2009) Rapid photochemical production of ozone at high concen trations in a rural site during winter.

Nature Geoscience , doi:10.1038/NGEO415.

49

### Dr. Yousheng Zeng

Urban Network Design Requirements

In my opinion, it is appropriate to require at least one monitor in a small MSA (population 50,000-350,000) where no design value exists. Howeve r, if after a period of monitoring, the results are far below the ozone NAAQS, state ag encies should be allowed to discontinue monitoring in the area. I would propose the fo llowing monitoring requir ements in a sliding scale. In a MSA with population betw een 50,000 and 350,000, a minimum of one ozone monitoring station be required to collect valid mo nitoring data for at least one ozone season. If the maximum concentration during this seas on is below 50% of NA AQS, agencies may discontinue the monitoring until the MSA is bumped up to the next MSA category (i.e., 350,000- 4,000,000) based on decennial MSA rede finition. If the maximum is equal to or above 50% of NAAQS, the monitoring must be continued for at le ast 3 years (3 seasons) to establish a design value for the MSA. The screening value of 50% of NAAQS is proposed as an example. Another screening value similar to this one may be establis hed based on a static analysis on probability of design value being higher than 85% of NAAQS if one year maxi mum is below that screening value. If the design value is below 85% of NAAQS, the monitoring may be discontinued as EPA currently proposed. If the design value is e qual to or above 85% of NAAQS, the monitoring must be continued until the design value dr ops below 85% of NAAQS for additional 3 consecutive years.

In regard to deployment schedule, I would propose the beginning of ozone season in 2011 instead of Jan. 1, 2011. This will give some agencies more time to install the monitoring stations without losing usable data. I also strongly suppo rt the idea of staggered deployment schedule. Agencies should be required to deploy at least one newly required monitoring station in the first required season within their jurisd iction (and one in each subsequent season if there is more than one newly required station). In combination with above proposed sliding scale, if an agency deploys the first station and the result for the first season is below 50% of NAAQS, the agency

can relocate the station to th e next newly required station. With this requirement and deployment approach, transportable monitoring trai lers can be used to maximize resources and

minimize cost.

Non-Urban Network Design Requirements

I agree with Dr. Hopke. It does not make sense to require a small state like Rhode Island and a large state like Montana with large non-urban ar eas to have equal number of monitors. EPA should develop different netw ork design criteria and guidelines. They should include considerations of geographic cove rage and level of ozone precur sor emissions in the area. I would also add the concept of sliding scale and staggered depl oyment schedule outlined above. To cover large non-urban areas, EPA should consid er requirements that would incentivize state agencies to use transportable (or even mobile ) monitoring platforms. For example, a state agency can use one or two transportable monitor(s) to cover a large area by rotating them at predetermined locations, one location per ozone seas on. If the monitoring result of a season at a location is below 50% of NAAQS, this location is screened out. With a combination of the

50above proposed sliding scale and staggered deployment schedule, state agencies can assess large areas in a very cost effective manner.

I support the option of using existing monitoring stations (e.g., CASTN ET monitors) to fulfill part of the new requirement.

Ozone Monitoring Season

I support the proposed increase in length of mon itoring period. The monitoring period should be long enough so that there should not be ozone ex ceedances outside of the monitoring period. My only question is how confident EPA is in maki ng this proposed requirement when only 45% of year-round monitoring data was analyzed.

I strongly agree that ozone monitors at NCor e stations should be operated year-round. I don’t know if PAMS stations are require d to be operated year-round. Th ere is some value to operate PAMS monitors year-round. This is not limited to ozone monitors at PAMS sites, but also applies to other pollutants. For example, if speciated VOC, along with ozone, are monitored year-round, it may provide some insight in ozone study, which is a major objective of PAMS network. In non-ozone season, sta tionary industrial sources of VOC typically emit at the level comparable to that of ozone season. These VOC may have a longer lifetime in the atmospheric during non-ozone season than during ozone seas on. Without strong atmospheric photochemical processes, the monitoring data during non-ozone season may pres erve sources’ characterization

and influence better.

Making the change to monitori ng period effective in 2010 for existing monitors seems feasible to me. However, more weight should be give n to several AAMMS members who are more involved in SLAMS operations and ma y know some practical challenges.

51

### Dr. Barbara Zielinska

Urban Network Design Requirements

1. Considering the ozone minimum monitoring re quirements that are already promulgated through 40 CFR Part 58, is the considered change to these requirements sufficient to ensure a minimally adequate network in urban areas?

The proposed addition of one ozone monitor in urban areas with popul ation between 50,000 and 350,000 is clearly appropriate in locations where ther e is an absence of an ozone design value. However, if after 3 years of monitoring a resu lted design value is lo wer than 85% of the standard, the state should be a llowed to remove or relocate the monitor in such areas.

2. We are considering a timeline that would re quire newly required ozone monitors to be operational no later than January 1, 2011, based on the expectation that final rulemaking will be completed in 2009. Is this schedule appropriate or should EPA consider providing an additional year for new monitors to be deployed (or re located)? What would be the advantages or disadvantages of a stagger ed deployment schedule?

I am in favor of a staggered deployment schedu le, especially when a new monitoring site is required. It is better to allow more time for purchasing adequate equipment, operator training, establishing QA/QC procedures , shake down period, etc.

Non-Urban Network Design Requirements

1. We are considering a new requirement that each State operate a minimum of three nonurban ozone monitors to meet certa in objectives (described abo ve). Considering the stated objectives of the non-urban ozone monitoring requir ements, is three requir ed monitors per state sufficient?

This depends on the specific State - one size does not fit all. Considering differences in a State geographic locations, presence or absence of protected areas downwind of major urban populations, sensitive vegetation, etc, , three non -urban ozone monitors may be sufficient for some States, but for some – may not. I suggest mo re detailed analysis; similar to that EPA has done for changes to required oz one monitoring season (T able 2 of the ozone review document). Variable patters of ozone tempor al distribution in complex mountai n terrain point to a need for higher number of monitoring sites in such areas th an in other areas (Van Ooy and Carroll, 1995).

2. What factors should be considered in the si tting of ozone monitors to assess impacts on ozone sensitive vegetation in national parks , wilderness areas, and other ecosystems?

One of the most important factors is to consider the presence of the most ozone sensitive species in these areas. For example, Ponderosa pine, wh ich is the main tree species in Sierra Nevada Mountains, is very sensitive to ozone exposure (B ytnerowicz et al., 2003). Thus, it is important to situate the monitors in proxi mity of these species during thei r physiological ac tivity and active

52uptake of gases. In addition, factors such as transport from large urban areas, enhanced photochemical activity in some areas, logi stics, etc., should be considered.

3. In addition to the objectives that have been described for non-urban ozone monitors, what other objectives should be consid ered in the final network desi gn? How would the consideration of additional objectives, if any, effect the minimum number of non-urban required monitors?

Additional objectives may include testing and evaluation of ozone models, ozone forecasting improvements and better understanding of po licy relevant ozone background values.

4. Current ozone monitoring regulations (described in Appendix E of 40 CFR part 58) include requirements for station and probe siting (e.g., ver tical distance of inle ts, set-back distances from roadways). Are these requirements (t hat have been developed for urban monitors) appropriate for non-urban ozone monitors? Wh at changes, if any, should be considered?

The additional requirements for non-urban ozone monitors may includ e appropriate distance from high trees and local roadways, placement of the monitors in open terrain and in proximity of sensitive vegetations.

5. We believe that States should have the opti on of designating that existing non-urban ozone monitors that are potentially operated by anot her agency (e.g., CASTNET monitors operated by the National Park Service) be utilized for meeting certain non-urban minimum monitoring requirements. What factors should States use to determine if such m onitors are appropriate to

include in their networks?

These monitors should meet the required tec hnical quality and be able for continuous ozone monitoring. Integrated methods (such as passive ozone monitors), are convenient is some situations and may help in selec tion of “hot spots” where real time monitors should be placed (Arbaugh and Bytnerowicz, 2003). Diurnal variations in ozone concentrati ons are important in assessment of the ozone impact on sensitive ve getations. Real-time monitors which can be placed in remote locations (light, reliable, batt ery-operated; not requiring AC), such as 2B Technologies, Boulder CO, should be considered.

Additional comment: Efforts leadi ng to a development of more biologically relevant ozone secondary standard, such as those taking curr ently place in Europe should be considered (Matyssek et al., 2007).

Ozone Monitoring Season

1. We are considering changes to the required ozone monitoring seasons based on analyses of the patterns of ozone exceedances and occurrences of the Modera te level of the Air Quality Index, during periods outside of the currently re quired seasons. What other factors should be considered, if any, in the determination of the le ngth of the required monitoring season for each

State?

Some sites, especially at high elev ations, may have only seasonal access.

5354 2. We believe that ozone monitors that are locate d at NCore stations should be operated on a year-round monitoring schedule. Under what circ umstances might it be a ppropriate to require year-round monitoring at other stations beside NCore?

The year-round data from some urban monitoring s ites may be important for ozone health effect study.

3. We are considering that change s to the required ozone monito ring season be applicable to existing monitors beginning in 2010, one year ahe ad of the deployment schedule for newly required ozone monitors. Is this sc hedule reasonable for existing monitors?

Yes, it seems reasonable.

References:

Arbaugh, M. J., Bytnerowicz, A. (2003) Ambien t ozone patterns and effects over the Sierra Nevada: synthesis and implications for future research. In: A. Bytnerowicz, M. Arbaugh, R. Alonso (eds), Ozone Air Pollution in the Sierra Nevada: Distribution a nd Effects on Forests, Developments in Environmental Scien ce, vol. 2, Elsevier, Amsterdam, 249-261.
Bytnerowicz, A., M.J. Arbauch and R. Alonso (20 03): Ozone Air Pollution in the Sierra Nevada:

Distribution and Effects on Forest, Elsevier, 402 pp.
Matyssek, R., Bytnerowicz, A., Karlsson, P.-E., Pa oletti, E., Sanz, M., Schaub, M., Wieser, G.: 2007, Promoting the O 3 flux concept for European forest trees. Environmental Pollution

, 146 (3): 587-607.
Van Ooy, D. J., Carroll, J. J. 1995. The spatial variation of oz one climatology on the western slope of the Sierra Nevada, Atmos. Environ. 29
, 1319–1330.